Well....you can count on 1 hand the # good 10ks in North America. This is one of them. So it is a precious opportunity that it seems a number of atheletes blew (or for which they were simply not prepared).
I would hazard to guess they went thru 5k in ~14:20? Maybe a little faster? No idea. The guys at the front were not trying to shoot their wad (Rupp etc). Its the guys further back - if you are a 29ish 10k runner, you will NOT get a field and conditions like this too often.
As for Hall...he himself said he was prepping for London. Ok...it will be interesting. KK couldnt break 24 for 8k 3 weeks before he ran a 2:05.