I guess the line of thinking is "the more differences there are, the leakier the abstraction is". The obvious case people will think about is the security angl

I guess the line of thinking is "the more differences there are, the leakier the abstraction is". The obvious case people will think about is the security angle (by using a vm you to impersonate a consumer end user, so for eaxmple malware doesn't realize it's running in a vm). But there are other cases where murphy's law will bite you. For example I bet some WebGL apps manage to trip themselves up over this feature string because of whitelists or buggy logic in code that tries to be clever about used features vs underlying platform.