Is that when the + command was overridden in search to refer to G+ instead of 'this is a mandatory search item'?

I am still shocked they ever thought that was a good idea, or that surrounding quotes was an acceptable replacement.

No, when that was changed you could at that time just quote a single word to get the old +word behavior.

Years ago when I interviewed for a Software Engineer position at Google, the person I was matched to eat lunch with between the interviews was from the Search team.

I asked him these exact questions. He said, the last time he checked, quoting a single word to mark it mandatory worked for him and that he definitely would know if it didn't.

I didn't insist much at the time but I knew he didn't know what he was talking about, and it made me lose hope that this feature would ever come back working like it used to.

Are you saying the quote-a-single-word thing doesn't work for you?

It has not been a guarantee for several years, now. At best it seems to be a slightly firmer suggestion.

Do you have some example searches?

I believe you, just never seen it myself. Perhaps I switched some obscure setting on years ago.

None that are guarantees, unfortunately. It's maddeningly inconsistent from day to day. But it isn't that rare, either. I only perform 10~20 searches using the quote feature a day, and I hit a case where it's ignored several times a week.

Doesn't work consistently for me.