Not in the way you're most likely imagining. You must explicitly set which device is the one-and-only fitness tracker for your Garmin Connect account. You can manually change that in Garmin Connect from the vívosmart‑HR to the vívomove and vice versa, but if you do so in the middle of the day (or evening), there are consequences for the tracking data retained/presented.
Any plans to change this behaviour, do you know?I don't know, but at a guess, probably not.
Surely having users buy more devices is a good thing for Garmin?Of course, but more in the manner of a customer having one device in the vivo family for 24×7 activity tracking (which provides rudimentary – if at all – GPS/performance metric tracking for specific sporting activities), a Forerunner or fēnix watch for running (and maybe swimming, if we're talking triathlon/multi-sport models), an Edge computer for upfront display mounted on the bicycle's handle bar, etc. as opposed to multiple 24×7 activity tracking devices to suit different social/everyday occasions and style requirements.