Even spinning you need some resistance. I have also had to lean more towards spinning when recovering from an injury/illness - for example instead of standing up at the top of a climb like I prefer, I'd just granny gear all the way - but you can't be in such a low gear that you're just flailing your legs with no benefit.

EDIT: for some reason I was thinking more about recovering from injury, etc, not a typical recovery ride(maybe because I'm recovering from injury myself. Anyhow, same thing, you need some resistance. And recovery rides should be easy and fun. Sometimes I even take a different bike than numero uno, go somewhere flat and chill . . .