Double quotes hasn't worked in a long time. It used to be the case that if you search "foo" "bar" it would only return documents that had the words "foo" and "bar".

I will frequently search for z foo bar z, get documents that have synonyms of foo and bar (and the synonyms will be highlighted in the snippet), then I will search "foo" "bar" and get the same documents except now it doesn't highlight the synonyms in the snippet. Maybe I am in some awful cohort where this feature is intentionally broken to see if it reduces engagement.