Harry,
Excellent points. Thank you.
So, it really boils down to if you re-installed from scratch or if you installed in parallel.
I the most recent upgrade I was involved, from 15.0.3 to 15.7, we just re-installed on a parallel host, OS, and created the instance from scratch, seeded it with dump and load and swapped the IP address of to the parallel box (and some other things) to go live on the new box.
Bottom line, we did not notice the problem! LOL. But, good to know.
Regards,
Jean-Pierre