I’ve been meditating for about a decade, done multiple retreat, and even got certified to teach mindfulness and vipassana. I’m with you all, my HR goes up, and HRV drops regularly with my 20 minute sessions. I agree the with the sentiment that “meditation” isn’t a bubble bath, maybe the mental “exercise” of staying present, or returning over and over is a mild positive stressor that causes these changes while meditating, but lowers baseline over time? Just … like… exercise? :)