Skyw had even more 700s than posted above come off contract for United at the end of 2015. They could easy be all SKYW planes getting parked. Most of them are still flying on short term extensions for United, while a few will be rebranded for American flying.
I'm guessing United wants to keep some around on a short leash so a.) They want to see how staffing shakes down and b.) they may be playing plane-and-pilot keep away from their competition.