"most of the time easy" ... = z2. z1 isn't going to lead to any adaptations (or burn many calories, depending on your objective), and z3+ isn't "easy", so for all your agita about San Milan & Attia you're basically saying the same thing.
Or to tie this into running, too, the same thing Maffetone & Friel also espouse.
Or to tie this into running, too, the same thing Maffetone & Friel also espouse.