Thanks for the replies, everybody. I live/train in Chicago, so low altitude and everything flat. RPE didn’t match heart rate at all, but I checked my HR with a stopwatch and got the same numbers.
All of that said, I got a pretty bad cold over the days following the workout I mentioned (still trying to get over it), so I suspect this was all just a consequence of being sick and not knowing it yet.
Thanks again for engaging, though.