Your poll is too narrow... or maybe I am supposed to choose "Bastard"?
The answer is "to an extent".
Balance, counter-balance, opposition of force, hanging from straight arm, pushing rather than pulling... all these basics can be learned in a gym environment, there is really no doubt about that...
However, technique... or that part of technique one might say is "reading the rock"... that, is in very short supply in your average gym rat, and can only be gained from mileage on real rock... it's why we see recently emerged gym rats crimp their way up 5.8 crack, or just outside the crack...
And, I'll add I think gym climbing is pretty weak for "endurance" IMO... I don't care how many 5.11 30 foot routes you can do in an evening session... that doesn't translate well to even a moderate Grade IV like Solar Slab, Johnny Vegas, or other long MP routes...