Just to be pedantic
DefMet’s task if purely measurement (defect metrology) knowing where, what type, how many, and what severity (ki-ler vs non impacting) the defects are. Purely the eyes. DefMet doesn’t improve yields or get processes production ready.
DefRed (defect reduction) on the other hand takes those measurements and is supposed to get them improved and transfer ready.
Now I suppose if DefMet has problems it could influence ramp. It is hard to drive with your eyes closed or while you’re hallucinating