In the past that Google search returned no results for any search. Today the set of results are altered before they are presented to the user. Sometimes the set of reslts is empty and at other times it contains results.
For example:
steve -steve returns 0 results
test -test returns 4,780,000,000 in my search
starting with google/youtube videos
That's easy; there are synonyms added for test but not for steve.
If you search for ["test" -test] you'll get no results; quoting "test" removes the synonyms.
It's probably not new behavior per se, but synonyms have gotten a lot broader over the years, so it was a lot easier to punch [term -term] ten years ago and hit a term which had no synonyms.
Correct, though it is new in the sense of this conversation, which compares to how a search used to be.
The point wasn't as to what the synonyms were for a specific search term but that they have been added as implicit terms, which makes google search no longer exact.
I mean, I'm confident that the core of how it works -- "an exact match between the tokenized document and the tokenized query" -- hasn't changed in a very long time, but I can't really promise there wasn't another aspect I'm ignorant of that is responsible for the behavior you remember that changed somehow.
"Exact tokenized matching" can look like "exact string matching" a lot of the time. Until you hit some of the edge cases it's like kerning: https://xkcd.com/1015/
For example: