I can also confirm your AC t-mobile account will only allow 1 simultaneous connection if you have a solo AC account, or 2 simultaneous connections if you have a spousal AC account.

You have to specifically click the "click her to disconnect" link that pops up in your browser as well to switch to another device, or you will have to wait for some sort of really long timeout.

On a side note, last time Mrs. Azulcactus went into the AC by herself, they mentioned to her they were splitting spousal accounts so she is now under her AAdvantage number, and I guess now we are linked for the EXP and spousal discount. The upshot is we get 1 simultaneous connection now for each of our AAdvantage numbers. Same difference I guess, I just found it interesting.