Who ever said he was as polished as Bibee? It certainly wasn't me because I've blatantly said that Bibee was the most polished SP prospect we had. Thing is, Williams doesn't have to be as polished. Sure, it would help like it would help any pitcher, but he is so overpowering that he can be very effective without pinpoint control. He simply hasn't really been challenged yet and I don't expect that to happen until he gets the call to Cleveland. Don't forget they view him as an option right now and if someone goes down or gets dealt then he's the next man up.
I think most of us are just as high on him as you (other than SC say Cantillo is higher than Williams - as Bimbo just said Cantillo needs to adj to his body growth but in their ballpark of talent). But, there comes a time where you just don't turn over your roster 180 over night with 3-4 other trades to make room (not enough scouts to look over tapes on returns). I think Williams gets rostered by year-end (even though they need to save 1 or 2 prospects till next year to avoid Rule 5 issues but another argument). You also want to create a bit of room between these guys for contracts and FA issues down the road (but few months ain't big deal I guess). But, more importantly, you don't want 3 rookies in MLB withing 1 month as you don't know their consistency yet to go 6-7 innings consistently that we know Bieber, McK ( when back) and Civale(5-6 range) can ...
By next May (if not sooner), I see a roster of
SP(5) - McK, Bibee, Allen, Williams and ..... (choose 1 of 4 - Beiber, Quantrill, Plesac and Civale)
RP(8) - Clase, Stephan, Morris, Hentges, Karinchak (demoted role), Morgan, De La Santos and either Sandlin/Herrin/Battenfield (for length)
Catcher(2-3) - Naylor and either Zunino (resigned) or backup defensive catcher like Gallagher or Collins as a sleeper (DH possible)
Infield(5) - Ramirez, Gimenez, Freeman/Rochhio, Naylor (Collins can slide into 1st as well) (Question if Bell is around or opts out which he isn't right now)
OF(5) - Kwan, Straw, Valera, Oscar and Arias (filling in everywhere) - no Brennan????
Your 14 others (on roster)
Pitching(8) - Espino, Cantillo, Curry, Battenfield, Gaddis, Hankins, maybe -- Burns, Smith
Position(6) - Brennan (or Valera), Noel/Pries, Brito, Martinez, (maybe not Tena or Palacios but valuable for injuries)??? with Burgos and Frias maybe getting a slot
Just saying, there is a lot of moving pieces to get everyone in that deserves a spot ... but to trade even 3 of 4 of Beiber, Quant, Plesac and Civale plus Rosario plus others by July AINT going ot happen to get Williams up with Bibee and Allen at this point. Heck, Rocchio is hitting the snot out of the ball and Rosario hasn't been traded yet (think I heard 21 out of 22 games played he has had a hit). Yes, they did 14 rookies last year ... yet, they are going to slow down a bit (just IMO).