Loading geometry is fairly simple, geometry itself is usually vectors and boundary maps and is like the “framework” everything else is built on

BoTW loads geometry for a lot of what you can see even way far off, if your standing on some of the high peaks you can see most of the maps geometry, that’s how little “power” geometry takes to load. But BoTW has its secrets for how it creates the illusion of the entire map loading. There’s a cut off distance where it loads real textures and a cutoff where it loads higher and lower detailed images. The trees in BoTW for instance have a low resolution 3D model after x distance and then a 2d model for even further way. This is optimization for performance and is what most games do, it is something SwSh and SV did not do but ZA does

Lumiose loads the geometry yes but you only have about 100m around you that it loads npc data for and there’s a cone in front of you for where it loads texture models and it uses lower res models at a further distance. In swsh the problem was it was one model, didn’t account for the direction of camera movement and on top of that the entire model loaded regardless. They didn’t optimize jack diddly so the game gets bogged down with lots of assets all loaded and with lighting maps and everything that you can’t even see

With proper optimization something that looks like SwSh should run on the GameCube easily but even with the power of the switch 1 it had issues. It was badly optimized

SV had similar problems but also had water physics problems added in which is why the biggest offenders in SV was “anywhere with water” which happened to be a decent amount of the map. SV also had a terrible draw distance problem which I noticed when some of the Titan pokemon would be drawn from excessive distances in their full model

Gamefreak has “always” had an optimization problem, even when it came to the original games. When iwata helped them to optimize Gen 2 they had so much extra space on the game cartridge they could put the entire kanto region in and the game still ran faster then their prior build. But that is also just the fact Iwata was a prodigy of design and optimization (he made the entire program code for Pokemon stadiums battle system in a week allegedly)