So I take that I can panic if I need to.
Maybe the "confusing" thing which the docs warn about isn't reporting an error. I believe that Deref::deref should be stable as long as Self isn't explicitly modified in some way. I.e. deref's return value and panic-behavior should not change unexpectedly (e.g. due to an I/O error) but may change after explicitly changing the contents of a Box, for example.
Like I said above, maybe the key point is some sort of "stability" rather than reporting error states? But not sure.