AA assigns flights to certain gate areas on a 'planning' basis. For example, all international ones fly in and out from Term D.
I travel DFW-MSP requently and they tend to use the high Term C gates for these flights.
There is a plan.
what happens the day of your flight is anyone's guess as this 'plan' can go all to heck.
BTW AA uses Term A, B, C and D .. they do not use Term E.
PS ... why two LAS flights close together? demand!