> We found files shown earlier in a PR to receive more comments than files shown later

I often stop reviewing a PR if I have too many comments on it already that need to be addressed so I wouldn't say this is necessarily what it sounds like (later files get less attention). Also, a comment on an early file might address a concern in a later file that will be fixed by the time I actually review the later files.

That said, keep your PRs short and you won't have to worry about stuff like that.