Besides, what's the big deal if a parent accidentally buys the wrong one?
The problem isn't that parents can't tell them apart so they buy the wrong one.
The problem is that parents can't tell them apart so they buy one and then never buy any of the others because they're 100% confident their kid already has the gray and gold dinosaur.
No, the problem is you conveniently left out the rest of the paragraph you quoted, especially the very next sentence:
....The kid will know the difference instantly. That's what reciepts are for! Just return it for the right one. And by-and-large, likely the only time that a parent/adult would be toy shopping for a kid without said kid being with them, would be at X-Mas or for their birthday, or any similar special occasion.
Mommy comes home and says "Here, Billy. This is the one you wanted right?"
"No, Mom, that's Slag! I already have him, see. I need to get Snarl, the stegosaurus."
"Ok, well we'll go back tomorrow and see if they have the right one. ok?"
It's not as if said parent is not going to try and get their kid the right toy. You make it seem as if people will go and buy only one figure, and the kid be dammed if he already has it, or it's not the right one.
This is why stores have return policies in the first place.