Hokay! So, the
next chapter of the New Legends manga just dropped and is officially retconning the Japanese dub of EarthSpark as being an alternate divergent timeline to JG1 that split off from the main timeline right before the first episode of the G1 cartoon, four million years in the past.
Basically, Alpha Trion hears about Optimus Prime's plan to leave Cybertron aboard the Ark and travel the stars in search of new energy resources, and that Elita One won't be able to go with him because, according to Optimus, it's too dangerous for her to come along (which we saw in a flashback in the G1 episode "The Search for Alpha Trion"). Alpha Trion then reads from the book of prophecies, the Covenant of Primus, to see what the future will look like if Optimus embarks on this trip to the stars; the Covenant foretells that Optimus will not return to Cybertron for another four million years.
Wishing to create a future where Optimus and Elita can remain together for all time, Alpha Trion uses the Quill to write in the Covenant of Primus and create an alternate future timeline where Optimus and the Autobots do not leave Cybertron aboard the Ark, instead remaining on Cybertron and toughing it out through the war for the next four million years. After which, the war finally shifts to Earth with neither the launch of the Ark and Nemesis nor the four-million-year slumber of the Autobots and Decepticons inside the Ark. This is meant to line up with how the war's events were told in the EarthSpark cartoon.
Once the war comes to Earth, the events of EarthSpark's version of the war plays out, with humans getting involved, Megatron reforming and siding with the Autobots, and then the show's present-day events play out. But during the time that passed before the war came to Earth, the language of this divergent splinter timeline deviated from that of the main timeline, meaning Convoy became known as "Optimus Prime", Cybertrons became knowns as "Autobots", Destrons became known as "Decepticons", and so on.
But of course, all this is just a splinter timeline while the original timeline of the G1 cartoon and its many, many Japanese sequels and spinoffs remains unaltered. Japanese EarthSpark is now a timeline split because Alpha Trion wanted to write some OptimusXElita fanfiction.
Meanwhile, the original English-language version of EarthSpark remains its own non-G1 continuity, basically like another "Car Robots vs. Robots in Disguise" situation, or "Galaxy Force vs. Cybertron".