>>37801791I'd say your pretty much right but Mt. Coronet is not a corridor it's a relatively complex map by Pokemon standards and the multiple entrances, exits, and the constant retreading through it at different points of the game was pretty confusing for kids.
The thing about old Pokemon that tricks people into thinking it's more open is that you're taking up one tile and then the camera is far back showing you a wide area. With the 3D games while the design philosophy isn't different the areas are a bit tighter and the camera is close in. It makes areas feel smaller than they are. On top of this in the first five gens you moved relatively slowly, while gen 6's rollarblades and gen 7's faster run let you traverse areas in a quicker time and that makes the games feel smaller.
I would suggest taking a beaten LGPE and RBGY game and clock how long it takes you to run a lap around Kanto and see just how much speed changes the experience.