Later it didn't seem to be regenerating, but I swear, those first couple of rooms he was regenerating hp.
My overall impression of the guy is that he does speed runs of games because he can. He'd never played SR before that video and likely hasn't played since.
Oh, and 45 minutes for 5 floors is super standard. I did it last night. I had a few pauses (responding to IMs) and did some optimization back-tracking, but total run time was still about 48 minutes.