>>28129765It's not an issue of space, you could easily fit RBY's Route 23 in GSC, it's an issue of time. There's data for a bunch of beta maps they could remove to make more space, including what some people believe is a longer beta version of Route 23.
It's true that GF had trouble even fitting Johto into GSC and Iwata cleared space, but after he cleared that space you'd have no issue. The reason Kanto is so chopped up in GSC is because this happened shortly before release and they didn't want to delay the game again after three years of development.