I never had any faith in a TP oil filter as the paper is biodegradable and I worry about the paper disintegrating and plugging something if moisture collects in the oil. I used to see Frantz Oil Cleaners on automotive engines in the 60's and 70's, but I haven't seen one in use in quite a long time and I don't remember ever seeing one used on an aircraft engine.
I have 7 Frantz filters installed on a variety of engines and automatic transmissions and some have been in use on the same engines for 50+ years without any negative effects. Although I haven't tried it, others have used TP to filter engine coolant very successfully. ...
As a side note, I just recently posted a thread with photos of my Motorguard using TP as a coolant filter in this very forum.
FAA approval simply means that they were adequately convinced it wouldn't cause problems if installed and operated properly. It's no reflection on the effectiveness, or lack thereof of TP as a filter.
That said, anyone who would choose no filter at all over a properly installed and maintained Frantz TP bypass in a GA aircraft should have his head examined, and probably shouldn't be flying.