It's potentialy a nice feature, but thus far, at least for myself, it doesn't work. My HR comes down 30 or more in 1 minute and usually another 15-20 in 2 minutes. Garmin is using a 2 minute test period and each workout only shows "5 bpm" recovery after each, which is not correct.
I've reported it to them, and the engineer they have assigned to this doesn't seem interested in even having a discussion.