While, yes, the whole Primus layer was indeed a big fat retcon, what Takara did with their version of Vector Sigma was basically reconcile all of the different interpretations of it featured across the different series of the Japanese G1 timeline:
- Vector Sigma of the G1 cartoon: The ancient ultracomputer that gave life to the Transformers, hidden deep within a secret chamber near the center of Cybertron (listening to the dialogue of the Japanese version, it sounds like Megatron at one point refers to Vector Sigma as "kami", meaning "god")
- Vector Sigma of The Headmasters cartoon: The ultracomputer that maintains the balance of stability on Cybertron, which is also somehow tied to the sacred cosmic power of the Matrix (Note that it is also supposed to be the same Vector Sigma as the first one, despite its bluer appearance inside a very different-looking chamber)
- Vector Sigma of the Beast Wars Neo cartoon: The "God of Cybertron" said to have been the Transformers' creator, now a known public figure and the highest authority on Cybertron, residing high up in the Tower of Light (and now speaks with a female voice and has a completely new look as a silver, jagged, crystalline shard, coincidentally looking kinda like a giant version of the AllSpark shard from ROTF)
- Vector Sigma of the Car Robots cartoon: The "God of Cybertron" like in Beast Wars Neo, now said to have bestowed Energon Matrices to those of the Convoy Class, and is said to have created a great fortress called Cybertron City hidden on Earth in ancient times to protect something called "Gaia Energy"
- Vector Sigma of the Beast Machines cartoon: The ancient computer that eventually evolved into the Oracle by the time of the 24th Century, and has only just been rediscovered after having faded into complete and total obscurity over a long period of time, with only its evolved Oracle form being remembered in legends (legends that said the Oracle foretold the coming of the Transformers to Cybertron), while knowledge of its original Vector Sigma form remains confined to centuries-old datatrax (Note that while in the English version the Oracle speaks with a female voice, it speaks with a male voice in the Japanese dub)
Combining all of that gives us
Vector Sigma: The ancient computer hidden deep inside Cybertron that gave life to the Transformers after foretelling their first coming to Cybertron, maintained the balance of stability on Cybertron in tandem with the power of the Matrix, and was revered by the Transformers as their god. Following Cybertron's destruction in 2011, Vector Sigma somehow survived and eventually evolved into the Oracle by the 24th Century, during which it was rediscovered after a long period of dormancy that had led to its fading from Cybertronian knowledge. This rediscovery brought it back into public awareness and eventually led to its becoming the highest authority on Cybertron, by which time it had evolved again into a new form and started bestowing a certain class of individuals with Energon Matrices. Oh, and it made Cybertron City in the distant past and put it on Earth to protect the planet's Gaia Energy for... reasons.
Thinking more about this streamlining of Vector Sigma, when going back to what the Kiss Players timeline did, before adding in the Primus part, all that was added to this equation was just Primacron's assistant, in an attempt to explain the presence of the Matrix seen departing from the assistant's body in the episode. Since the episode's script referred to him as "the Oracle" (based on his glowing energy appearance), the timeline simply merged the two entities named "Oracle" into one being, which also merged the assistant with Vector Sigma since the BM Oracle was also a form of Vector Sigma. Coincidentally, both the G1 Oracle and Vector Sigma also had the same voice actor.
Though, since the G1 Oracle was also located on an ancient rocky planet, all scenes set on that planet had to be retconned as taking place in the distant past in order for this retcon to work. Watching the scene of the Primitives traveling to that world, it does kinda look like it could be reinterpreted as a time traveling sequence. This retcon also fit nicely with how Beast Machines said that Cybertron had originally been an organic planet, so the Oracle's ancient world would just be how the planet looked before that lush green ecosystem was created. And since the Key to Vector Sigma was already retconned by Beast Machines into being able to turn any and all organics into technomatter, that provided the perfect tool for the Quintessons to have built Cybertron with in this retcon.
Plus, what really brings things full circle is a nice bit of symmetry in how, in the episode, the G1 Oracle's planet was said to have been located at the center of the galaxy, and then later near the end of Beast Wars Neo, Cybertron was located near the center of the galaxy, essentially bringing the planet back to its origin point at the end of the latest-set JG1 cartoon.
And this is all still before the Primus part was added in, so even without that part does the retcon still look basically the same as it did back when it was first made in 2006/2007. I guess the Primus part was just added to try to give some real weight to Vector Sigma/Oracle being an archenemy of Unicron, since neither a space monkey nor a shiny globe would have seemed all that impressive fighting against Unicron directly during the final battle of the Sparkbots storyline.
And even though the Primus part was added in at the time, not much else was really done with that particular part of the retcon until 2019-2021, when Generations Selects really dove into JG1 Primus's backstory with the Primus Vanguard and the Precursor World. I honestly thought it was quite clever to use the Vector Oracle toy to represent his most basic, original form, since back when that toy was first unveiled,
my initial reaction to it was "Judging by his name, Vector Oracle may be a physical humanoid form of Vector Sigma."