So, an update. Did the PRP on Friday - decidedly unpleasant (painful). Then was totally sedentary for 48 hours (Saturday-Sunday). I was very sore from the PRP for about 6 hours after, and moderately sore the next morning. As of 5 days later, the attachment point is still a bit tender.
On Monday-Tuesday I swam some with a pull buoy and did some very gentle rehab exercises (nothing that hit the hammy specifically, just glute bridges). On Wednesday I went in for PT, and was told to shift to normal swimming, and then start phasing in the elliptical.
I went for an easy 3000 yards this morning - was going for 4000, but the hammy started getting sore, so I stopped. Interesting thing is that the hammy did NOT hurt when doing freestyle before the PRP, except for the occasional twinge. This morning, I definitely got some soreness radiating down the hamstring. Don’t know what to take from that - I do know that I’m still very early in the PRP response, so it hasn’t worked whatever magic it has yet. But uncertain as to whether I should back off on the swimming for a few more days. I have an email in to my PT to ask.