This is a really great exploration. I like what Alan Watts says about this problem-- that the point of the apparent paradox is to remind you of the ultimate inefficacy of language, which might shock us back to being present in the moment in zen.

Personally, I think that the easiest interpretation is the concept of the Bodhisattvas. They coooould be fully enlightened with no suffering and cease to exist in samsara. But they choose to stay to help everyone else achieve enlightenment too. Like perhaps they have eliminated all of their desires but the last one, which was to help people, and then once all the people are saved they will eliminate that final attachment too.