I really don’t think colleges are fretting over yield rates, nor bragging about them. Stanford stopped announcing acceptance rates. USNWR stopped using acc rate and yield in their rankings.
I think colleges use SCEA and ED simply because they would like to fill a significant portion of their class with students who truly demonstrate that it is their first choice. And there is nothing wrong with that. That this pushes yield up is an statistical consequence, not the objective of it.