Originally Posted by crackjack

No, I mean the situation seen here (selection of a PE seat on a Y ticket is likely occurring in a scenario where there are PE seats physically on the plane but no PE tickets being offered, e.g. hence 3 class plane but only 2 classes sold (or 4 classes physically but only 3 sold).

In that case, the operating airline is still trying to maximise the number of passengers on the plane, but also it makes sense to get something out of it, e.g. extra payment for the seat or an perk with which they can drive elite loyalty.