Um, no he doesn't. And it is not even close. Booker has an overall more polished game (skillset) for a post that we've in a long time. Booker has the athleticism of a 3 and the size and strength of a 4. Unless something mentally holds him back, Railey and Gibson are not near his level.
Edit: I didn't even see the second part of your sentence. Gibson's body is YEARS away from Booker's. Booker is the most cut player on the roster, and he's ~245...
Gibson has a bright future and I'm excited to see him fill out his frame but his offense is far from polished. Railey has size and we'll need that presence but his offensive game is even further behind Percy's. He literally doesn't know he has a left hand yet or what a 'post move' is.
To clarify on the CCL, few bigs play down low. White didn't. Booker didn't. When they did, they dominated, because there's really no one to guard them. Booker hung around the perimeter and made a ton of jumpers and made aggressive moves to the hoop on dribble drives, showing good handle for his size and good finishing ability with either hand. Again, it's a summer league. If he doesn't want to play the 4 at Iowa State when the season comes around, then he won't play as much and he won't reach his potential, an example of something 'mentally' holding him back.