Just another datapoint.
I was looking at BWI--DFW-ICN for next month, and also in March, as the trip dates haven't been firmed up. Both trips are about 10 days - leaving on a Friday and returning the following Saturday. In both cases, the plane's listed as a 789.
In Feb, PE isn't even offered for sale (just Y and C), despite the seat maps showing it with some seats occupied. So some folks got in there somehow. In March, it's hit or miss whether it's for sale. A Friday flight doesn't offer it, while a Thursday flight does. Usually if it's offered but sold out, it'll just say so. But not here. I let my EF subscription lapse as my travel fell off last year. So I can't look up codes yet until I renew.
My first thought was that not all 789's had PE, but seatguru and other reading here showed that wasn't the case.
If AA isn't offering it on the website, but the plane has it (and shows it mostly empty), is it something a travel agent or AA could book? I've experienced weirdness pricing tickets out before - especially to ICN - that a travel agent was able to ticket.