Almost everything you just said about time_t is wrong. time_t is signed,
and always has been (otherwise the 'end of time' for 32-bit time_t would
be 2106, not 2038). Also, time_t does not end at 2038 because nothing
says it must be 32 bits. Also, Python has 'long integers' which do not
overflow.
Also, I don't understand what you mean about use cases. The "use case"
is "dealing with anything which expects standard Unix time_t, for
example the Python standard library". The use case I have personally is
the program I was working on when I encountered the problem described in
this bug report. Also I think symmetry is a darn good argument. Why does
fromtimestamp exist if, as you claim, nobody uses time_t?