After browsing dictionaries and thesauri for about half an hour trying to come up with clear names for the two types of days you defined, I concluded that the best option is to call Recovery Days "Rest Days in which you're tired", and Rest Days "Rest Days in which you're not tired". I'm curious to hear if that works for other people.
Note: the best eliminated candidates for Recovery Day were "Chill Day", "Sloth Day", "Lazy Day" and "Slow Day"; the best for Rest Day were "Free Day" and "Aimless Day". These candidates wouldn't remove ambiguity.
I've met a university professor who asked me lots of questions, but avoided giving me her own opinions. I felt left in the dark and suspicious of her intentions. My impression was that she used her belief that heated arguments don't lead anywhere as an excuse to shield herself from judgment.
That said, I, like her, but unlike the OP, think heated arguments are indeed counterproductive. Ideally, each person should expose both what they know and what they don't know and aim to build on each other's ideas. I find discussions on LW to be good examples of what I mean. Of course, one needs to balance that ideal with status preservation, especially at work.