As someone who administrates a large tournament, there really is no such thing as "full" regarding one wrestler. Scratches and such can be estimated but you are always working with a fluid number, you may be full in regards to teams - which would add ten wrestlers - or multiple individuals, but one wrestler is NOT going to make you "over full."
There may be deadlines - no idea on how those deadlines have been enforced in the past by the Midlands - but turning down a single wrestler because you are full is just a nice way of saying you don't want them competing in your tournament. Could be because the wrestler isn't good enough to warrant the invite or the exception - don't think this is the case with Hall. More likely this is the Midlands exerting pressure on PSU, saying something like "you guys don't come here, you regularly go to our competitor, so we aren't going to help you out with this." Tournaments ARE in competition with one another and guys that run tournaments are generally competitive. I'm sure if the Midlands saw letting Hall compete as a gateway to getting PSU to compete in the future they would have let him in. They didn't, so they didn't. Which is understandable - not ideal, but understandable.