Spotlight UI doesn't surface folder and files that the mdfind cli tool locates

I installed Monterey 12.0.1 three days ago. I searched for a PDF basically by name in Spotlight and it couldn't find it. I tried again with a few other PDFs that I know on my system, but still no luck. I put in the exact name of a folder, and it didn't show up at all. Same behavior in the Finder search box. When I put the same queries in on the command line via `mdfind`, it found all the files and folders I wanted. I even tried reindexing by marking my entire home directory as private and then removing it again, but still it doesn't work.

After poking around a bit, it seems to have a problem with word separators: I can search "metaprogramming" and it will surface "metaprogramming-elixir.pdf" but if I put in "metaprogramming elixir" it doesn't show up. ("metaprogramming-elixir" works for some reason) Same behavior with "study" vs. "study_journal"—the folder is named "study_journal", and when I put in "study" it shows up in the list (along with lots of other results!) but it disappears when I put in "study_journal" or "study journal". (Seems underscores and dashes are not in the same character class.)

Seems to be a regression from Big Sur.