It has been available for a very long time without being shown. You have to corner the many overworked table clearers. I found it less of a hassle to go to the servers entrance and stand and knock on the door.
Covid and beyond had it out for self-pour, this is not the default state previously. Some lounges, like Gatwick does have, and some outstations (those which have it, I've seen that at Vancouver, but not Philly). But I believe last autumn went back in. You might also have better luck with the T5B lounge (and the underpass to walk back to A, if you need to, the transit does not go back), where the staff are considerably less overworked.
There was a time when there was sparkling white out in the self pour as well. I didn't see this, but it's probably still fine to go and ask for Champagne from the servers if that is true.