Newer APIs are also more flexible, making fewer assumptions about how things in the pipeline should run. E.g. the way a buffer clamps or overflows compared to the PS2 may be hardcoded in OpenGL 2.1 meaning you have to write emulation of that feature inside the older API to then run the code to emulate the buffer. In OpenGL the shaders types are limited in this manner, in WebGPU you can just use arbitrary compute shaders instead of having any assumptions at all about the rendering pipeline.

There are tradeoffs to selecting the older APIs just as there are tradeoffs selecting the newer APIs. Generally, the latter is easier on the implementation side for emulators.

That doesn't necessarily stop you from pointing an LLM at it and getting a working WebGL 1 version of course, it's just not a universal answer to "how should someone spend their tokens.