> Yes, and that lone call is never made in your scenario.
>
> So I'm no longer sure what problem are we discussing here.
>

The lone call to insert-file-contents, as in step 5 of my reproduction.
Calling insert-file-contents after typing in a file buffer runs the
after-change-functions hooks. When these hooks are run, the current
buffer's file name is seen to have been temporarily set to nil, which
should not be the case.

Is this clear?