Nobody seems to be dealing with the question asked in the original post, so I'll give it a shot. Why would the second ATG pass be more comfortable than the first? I'm also going to get a little heretical here and say that I don't believe it's the fact that the lather has been on the face longer. I've been using absolutely minimal prep for months now (after trying full, long preparation for a month and seeing no difference) and getting good shaves just lathering up quickly without even splashing water on my face. I'm not recommending anyone else do this and am not campaigning for it, but it can be done.

So, I don't think time with lather makes any difference. I'm going to put this out there: It might be that the second pass, with less actual work to be done, is a lighter, more careful pass, probably used for taking care of difficult areas and because these areas are difficult less pressure is used.