> Also, does the fact that YouTube doesn't supply a download feature constitute a "technical protection measure"?

My understanding is that basically anything at all, if it is in any way "technical" and shows intent, will be accepted as a "technical protection measure" if you go by what has worked so far.

Much more absurd and blatantly bad faith arguments have been accepted, "conspicuously not supplying the feature" is a very strong case in the absurd world of the DMCA cases.