I've never, never understood why Stephen chose to go this particular route. He's a smart guy, shrewd businessperson, so it just doesn't make any sense to me, especially given the reasons I believe he has stated.
If you think pressing is no big deal, but recognise that others do think it's a big deal, then when you press a book, aren't you eliminating them from the pool of potential buyers already? Not informing them - by virtue of "making them ask" is just a good way to ensure that all the people who don't like pressing are going to summarily eliminate him as a viable purchasing venue, even if he's got books for sale that aren't pressed. As he surely does.
I've never understood why people choose to make such a big honking deal out of proactive disclosure of pressing. How hard is it to say "Pressed while in my possession or purchased knowing it has been pressed? Yes" or "Pressed while in my possession or purchased knowing it has been pressed? No" in a listing?