>>42156163The games are locked to 30FPS, you can remove this lock and it'll run at full speed even in old as shit hardware so this means it was a design choice
Now the question is "why?"
My best guess is to give the overworld time to load properly
Sinnoh is a single map and the game loads the areas around the player in real time, if you go back and forth quickly between two loading zones then the game gets confused and fails to load the textures from the next area (AKA 'Tweaking glitch')
You can see an example of this in Any% speedruns
https://youtu.be/TRAf7shwSHI?t=3269 
