They offered the same deal to Kelenic and J Rodriguez, who turned them down (they're 4-5 on KLaw's list). Oddly, the better the prospect, the less likely they are to grab the relatively minimal security of a pre-MLB deal.
SD gave Taytis 14 years, and when all is said and done, they may be very happy they did. But damn, that's a lot of risk, and a lot of cheddar. So much time. So much can happen.