To the OP, and now that we're on the subject of :-: best in class :-: M fares, welcome to DL's way of doing business.

I have no skin in this because I'm never going to pay DL for an M fare.

I once spent $10 more than the rock-bottom minimum DL fare, because K class was cheap from LAX-JFK. Of course, the PMU was unusable in the end. No ug on status either. As I'd expected.

All I that I read and hear totally dissuades me from paying outrageous extra coin for M and the resultant UG gamble.

It means that those $10 are absolutely and totally the sum of marginal value DL will obtain from me over my lifetime as a consumer of their product. Never mind $1000s of more for a DL M-class fare than CO wants for actual Z business class fares. Astonishing!