I think part of the problem with the threads is most (if not all) threads we see now are cut
instead of the alternative of rolled threads, which are stronger and don't remove any material.

Of course as mentioned, many aftermarket pick-ups can't touch the bottom of the pan
to operate effectively.
The factory big block pick-ups are designed to have a little interference with the pan which
Ma probably figured out a looongg time ago helped add some stability to the connection.

My 2 cents...Joe