This is the same type of argument NGK makes with anti seize and we still see broken plugs and threads pulled out despite their coating.
Too much grease or anti seize on the spline shaft may cause an issue but a thin coating is generally not going to cause a problem. I don't care for the alternative of not using any, over the years I have come across some real bears.
Incidentally it seems no longer possible to get the Saab seal protectors you've previously reco'd. I tried last year and they canceled my order and said "never gonna happen" (ok I'm paraphrasing)
I'm still gonna try for the OTC or KM variants
