Given that the lens is about 40mm longer that the 24-70, and most of the weight is in the front elements, and the fact that the lens is used at up to 3x the max focal length of the 24-70, my guess is that it will be very difficult to manage on a ball head (using a sweet spot friction setting) without the collar.
Personally I think that if the pricing is fair then selling the collar separately is a good idea. Many of us end up buying replacement collars anyway. I have a 300/4 collar laying unused in a box. If I could have bought that lens without the collar for $200 less I would have.
By "fair" I mean that if the collar were included the price would have been $200 or more higher. We can only speculate on that, of course.
I think a collared 24-70/2.8 would be far easier to use on a tripod, even with my M20. I've always felt that the right way to shoot that lens on a tripod would be with a focusing rail (long rail + clamp oriented correctly), setting the camera body back a couple of inches.
These are just my own thoughts on these nose heavy lenses. I think the 24-70 is at the limits of a collarless lens, and although the weight of this lens is lower it is longer. The torque placed on the head may be the same or even greater. We will just have to see how people like dealing with it (without the collar).