Milone is a quality MLB starter already. Jury remains out on the other 3. Though Norris is already the A's starter behind the plate so he's close to locking up his spot as a full-time MLB'er.
I said they may not turn out to be special. I never said they wouldn't be competent ML players.
And I seriously question Milone being a quality pitcher outside of Oakland. His ERA was in the high 4's IIRC. Norris had a sub .300 OBP. Could one of them become studs? Sure. They might also all turn out to be the definition of replacement level players. That's the fun of following prospects.