I do think that there is a tendency to not give as much credence to the floor of younger players simply because we haven't seen as many of their flaws (if they do have them for example) as the guy in AA, thus they tend to look better than they may be.
With Yorman, I think the odds that he doesn't ever play in the majors (can't say with the Reds because you never know about trades) is less than 15%. He is a very good center fielder right now. He has great bat speed. He has a great arm. He will get his chances and move up simply because of those things. From there the question is, even if the bat never works out, does he at the very least turn into a 5th outfielder because of the speed and defense? It's a very different case for someone like say Juan Duran, who doesn't have the same defensive potential and has to rely much more on his bat developing to reach the majors.