> Herd immunity requires a much, much higher number than that

The jury is very, very much out on that. The 70% number bandied about is extremely naively calculated, it assumes 0 pre-existing resistance or immunity (Which we now know exists), and it assumes all humans are homogenous sphere-shaped balls floating around in a gaseous society, which is also obviously not true.

There are countless reports and studies on transmission among children in school settings, and they pretty much unilaterally state that there's very little spread happening there, contrary to everyone's "gut feeling" about kids being snot-nosed petri dishes.