Just flew with the new system and I was lucky enough to be able to talk to a CSA training SUP who gave me the low down.
Basically when they clear the seats the system will give you a seat. I got 1B. Then if there are other seats open that you would prefer the CSA can assign you that seat. Switched to 3C with the whole row open.
This took about 10 sec for her to do. Not hard. Super easy dont let them tell you they can't. If they can't its because they're lazy, hate pilots, or incompetent. Harsh words but I've been scwed many times by this type of CSA.
If you sign up for JS you can take a seat after boarding is done. FA will tell.you what seats are open via her iPad and then they relay that info to CSA or ops.
also FA can move a pax if needed. Same procedure.
no one can upgrade at the gate so if the seat is open it's open. Maybe that will chamge as I see SW leaving money on the table there.
This was easy but I can see it being a S show if no one knows what they're doing etc