Pretty routine to project a minor leaguer to some well known major league star, as sort of a best case outcome. For people who don't have the opportunity to see the minor leaguer, it's a way to visualize what the kid might look like.
That's a pretty big stretch IMO. If you think he is that good, which is, what one in a few hundred thousand? Why not say he is a fireballer with great command that will strike out plenty of people with accurate command? No way Giolito ever even sniffs Ryan's jock, even if it were filled with Icyhot.