As I said earler Frac, I don't think it can, but having just had the Acratech GV-2 delivered, and having had a good play, I have to say I'm mightily impressed.
Is the gimbal function a gimmick? Definitely not -I've been testing it with the max advised load which is a7D with battery grip, 300mm 2.8L , 2XTC, and 580EX flash hotshoe mounted. The head pans smoothly with that load and can be tilted to any angle with the touch of a finger and it stays there. It's a very fuctional gimbal head as well as a top class ballhead in it's own right.
Limitations? Because the camera isn't central over the centre of the tripod head in gimbal mode, it would be less stable in situations where you didn't want to spread the legs too much to keep a small footprint, (as is the case in some hides) but with a normal spread on the legs there's no problem at all.
To those who say that any ball head should be able to perform this function - don't believe it. I used to think the same until I tried it with my heavy duty ball head with the same load I've just subjected the GV-2 to. There's a world of difference between just putting the ball over 90 degs into that slot and continually tilting up and down with it. The resistance was obvious with the ball head and it's actually done it no good - it no longer slacks off the ball as completely as it did, although it's still perfectly functional. The GV-2 is designed to perform this function, having a large collar which fits into the 'U' slot and a short shaft at the other end of the ball which locates in a slot in the housing when in gimbal mode, so it's effectively rotating around a shaft when you tilt up and down.
I'll try to do a full review when I've used it in anger, but for now I'd have to say that as a 'normal' ball head it's first class, and that as a gimbal it works well for lenses up to around the weight of the 300mm 2.8L.