Having edged into Catalina through a series of beta releases, I have little direct experience with the release installer, but IIRC the initial installer gave a LIST of incompatible apps but they were not automatically removed. I do know there were additional 32bit executables (not apps) that were not on the list that had to be removed by hand. I found the Etrecheck/Etrecheck Pro Power User Package a big help in identifying and eliminating that detritus.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein