I never once told anyone to calm down nor did I tell anyone to stop being defensive. In fact, I never once said these were high quality leather cases. All I originally said was that I liked the patina that developed on someone's case and that patina will develop on all leather... I think you need to take a few minutes and re-read my posts.
I also did not put down his opinion. I said it doesn't make sense based on his observation, not that it was stupid or wrong.
Yes, the thin leather of the case will absorb oils but it will not be "saturated" with them. I also did not say it was impossible that the case could play a role in his experience, I just said it doesnt make sense.
What's more likely is that his hands may sweat more holding the leather case and thus more residue is left on the screen. When he took the case off, his hands may react differently touching the bare metal and now less residue is left behind.
That's possible as well, but either way the case would be the common factor and I'd need a case made of a different material in order to correctly use TouchID.