If you are proposing 2/30 there is zero reason for the Sox to do it as they already control those two years, and probably for massively cheaper than that. If you are looking at 3/45 you are buying out one free agency year for way below market, while paying WAY over market for the other two. Seems odd, but maybe depending on if the kid wants cash now, or a chance at the powerball later.
If you are talking 3 free agency years at $15 million a year, that is insanely low for Crochet to sign. If he has any self worth at all, for an offer like that, he waits another year at least. As Carlos Rodon proved, you don't need much in the way of health with performance to cash in huge in free agency.