Use of ... all are?

John, Bob, and Sue all are hungry.

The "all" is separable and not part of the subject NP but an adjunct in clause structure. This is evident from the fact that when the verb is an auxiliary, as it is here, it preferentially follows rather than precedes it, as in "John, Bob and Sue" are all hungry".

Note also the possibility of inserting an adjunct after the subject NP and before the quantificational adjunct, as in "John, Bob and Sue are certainly all hungry".