How long had Scotty been on Delta Vega? He could have been there a while, close to decade. Yeah, Jonathan Archer would STILL be very old. But people are assuming Scotty was just sent there. Even if previously Jonathan Archer went on to be a Federation President or an Ambassador he would have gone back to using his Starfleet rank while teaching at the Academy.
I like the reference. Even if you figure its a child or grandchild of Jonathan's its still an Enterprise reference. They did not have to do one at all.