only an arahant is fully enlightened. however anything below that is still a serious attainment, and those people could certainly teach the rest of us a lot! a sotapanna for example is guaranteed only seven more rebirths until full enlightenment! and so on up to non returning. if you reach one of these you have technically completed the path since they all guarantee final attainment but that doesn't mean you are perfect right after that attainment and before final knowledge.
personally though, if we are "speaking generally and don't make the distinctions" i would consider learning under a true sotapanna, sakadagami, etc. close enough
an example is ananda. he was only a stream enterer (sotapanna) prior to the death of the buddha. because of this he was not going to be allowed to recite at the first council! then he attained full enlightenment and they let him recite the sutta pitaka. if it was all the same more or less they wouldn't have bothered barring him based on not fully being enlightened.