How would this play out over time? Will sauna see a 3bpm drop below baseline on days it’s used, while keeping the same baseline?

Exercise, over time, should lower the baseline (to a point). I’d think this would have the more desirable long term benefits.

One can do both, of course, but when people see headlines like this they often jump to the conclusion that sauna can replace exercise, because that’s what they want to believe.

Due to lots of long distance running my rest heart rate is below 40. I am highly skeptical I would experience a 3bpm lower heart rate after sauna. Maybe this benefit applies after infrequent activity or less intense activity only.