There's a categorization here (I don't have access to the triage spreadsheet though):

https://github.com/ctz/rustls/issues/447#issuecomment-820719...

It seems like there's been the most effort on category 4, the ones that can't be reached but can often be proven away with refactoring and typestate. Removing these ensures that the APIs don't expose Result types to callers unnecessarily.

Category 1-3 have different severity, but they are all planned to be folded into Result error values.