I don't understand relying on official word* of a character's age to embrace a ship. Also, would his being 17 vs 18 vs 21 really make that much difference? Base your decision on whether or not you're 'allowed' to enjoy it on your own instincts, and be mindful of how your question, innocent though it may have been, can seem like condemnation to a contingent of fans already being shamed by some who don't like a particular pairing.

*The screenplay is as good as we're likely to get here