The other thing notable about those runs is elapsed time vs moving time - WG does seem to like to stop a lot! You can see when he stops as the hr plummets - but 200 reps aren't going to get your heart rate up appreciably anyway and definitely not with a stop in between reps.
The 4th June there is 6 min difference between elapsed and moving time, with lots of zero cadence sections on those hills. HR does look pretty normal for stop start run walk jog? Strava is frustrating because unlike Garmin it doesn't highlight where the run/walk/stationary bits are so it's a bit of guesswork working out where the stops were.
Don't think any of those runs show a similar pattern to the current one?