It's probably asynchronous reranking doing something weird. My guess is that the underlying ranking algorithms in these desktop search bars are very ropey, and

It's probably asynchronous reranking doing something weird. My guess is that the underlying ranking algorithms in these desktop search bars are very ropey, and they can't debug or diagnose because privacy reasons means the developers don't get to see what results were generated for different query/index combos. Also search is probably just not staffed most of the time.