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.

So many platforms with search have a variation of this problem now.

The other issue with Mac search is that it never tells you when it’s done, so you can’t tell if it searched and failed to find something or is still searching.

I find this theory pretty compelling: https://news.ycombinator.com/item?id=49703471

Maybe they are overthinking it.

Either same guy got promoted over and over again or someone thought we must copy this genius search bar as is