DY
I didnt make that assumption, PBA did. (I owuld think that if anything waiting would be stricter than nine days since the geder for waiting is moshech taam (see igros moshe i forget the teshuva exact mareh makom, but can find it tommrow on the rema/shach cited by PBA, wheras nine-days is simcha, but I do not have a mekor that say explictly compares the two.)
I assumed the opposite, that cooked in a dirty grill it shouldnt be eaten in the nine days, which is the way i remebered the halacha in OC.