It must have been a few years ago I did this for FB. Funny thing is looking at the map there are single tickets all over the place. Maybe they are leftover from a few years ago.
Their stance (or what they claim at least) currently is that you cannot leave a single when selecting your seats, but they can't prevent you from dropping singles or seats from your group during/as a part of your renewal. So they are saying, in theory, if you buy it, that all the singles you see available are seats that people have dropped at one point or another and not from people leaving those when selecting seats. I can't speak to the full validity of this, but in my anecdotal experience, this is how it worked for us this year. We couldn't add 4 seats from a group of 5 and leave a single either, but it was no problem for us to drop our two singles that we had last year that were/are separated by a seat between them as part of our selection. So two of the seats we gave up would now be available singles like you see a lot of places.
Tried calling in to combine my two pairs into 4 seats together and was unable to get the seats I wanted because there was 5 together. I continued to watch on the preview link yesterday and 4 of the 5 went as separate pairs leaving a single seat...
The first pair out of that set of 5 is fine/operated as expected as someone could select a pair from the set of 5 and leave 3 seats. If the remaining set of 3 then became an available single because they let someone else take just 2 of the remaining 3, then that's sketchy...