Thank you for sharing this. I too have noticed that on AA the SWU option doesn't show up all the time. For instance, I was considering a MIA to MAD flight on Oct 6th (AA68). Right now EF is showing C1 but when I look on AA.com it doesn't have the SWU as an option. A few days ago it was C4 and even then it wasn't an option. Ultimately, I decided not to book it because it didn't work best with my schedule.

I think the biggest thing to take away from this (for me) is to call before booking and just do it while on the phone. It's getting harder and harder to use and SWU in the first place so this is even more concerning.

Edit: I actually realized I wasn't logged in. When I logged in and searched it shows the SWU available. Still a bit concerning but at least I know I need to be logged in to see SWUs on AA.