It's only the cutting fin we're talking about here, it's very thin so it wouldn't take much friction to heat it up (because there's just not much mass there). OTOH, it's attached to a giant heat sink, so if the fin heats up it cools back down to ambient by the time you've finished flipping the blade.

I'm sceptical that heat has anything to do with it -- I suspect that speed and pressure are partially fungible -- either way the fin is hitting the leather hard.

One possible explanation for what some members are observing is that the bevel itself isn't stable over time. We tend to think of the business end as being "bevel" + "fin", but really there is a continuum between those two. The boundary area between fin and bevel may be warping over multiple shaves, and light pressure on the strop isn't enough to bring it back to sharp.

Or it's possible that unpasted strops are more abrasive than we've been giving them credit for.