"all but" is short for "all but < enumerated exceptions >". the speaker is just eliding the exceptions. people using it as an adjective/adverb phrase are just nodding at the whole thing, even though the exceptions wouldn't neatly fit grammatically. wouldn't be entirely surprised if it got smushed into a single new word over the years - albut or something.
"all but" is short for "all but < enumerated exceptions >". the speaker is just eliding the exceptions. people using it as an adjective/adverb phrase are just nodding at the whole thing, even though the exceptions wouldn't neatly fit grammatically. wouldn't be entirely surprised if it got smushed into a single new word over the years - albut or something.