My search habits didn't change in the last few weeks, only the results. Browsing as before, no VPN or private tabs search, always logged in YouTube. I don't have a Google account, just an YouTube account, but Google Search shows me as logged in, too, because I am logged in in YouTube. I know about double quotes, minus, advanced search, verbatim, put most desired word first, etc. Sometimes first quoted word was ignored, too.
This week was a little better, at least now I can see results from 2017-2019, too. Before, the results were mostly from 2000-2015 or so.
By the replies, it seems it was just me, so I was probably in a beta test program.