Rest assured that every single time that the camera focused on the crowd, the central sensor was very well on the rider or horse and the central sensor was selected as the only focus point.
I loved curves, long before Photoshop appeared
--Sorry for the pun - couldn't resist!
I agree with what you're saying: the faster the better. But until
we have an AF system that can focus in 0.01 nanoseconds, the best
solution for situations like rodeo is to have a dense array of
focus points with no gaps between them, aka Canon's 1-series
45-point AF.
There's a massive difference between the typical 3, 5, 7, or
11-point AF and 45-point AF: with 45-point AF, there is no part of
the viewfinder that is not covered by a focus point. So as long
as the object you want to focus on is the object closest to the
camera, you will always get a lock.
See the difference? With the camera setup in 45-point AF mode to
automatically focus on the closest object, you will never get a
shot focussed on the crowd like you did with your 10D - it's
impossible. The only problem you might have is that the camera
could focus on the horse's nose when you wanted it to focus on the
rider's face, etc. But the focus will always at least be close to
what you wanted.
With the 10D, you have to make sure that the AF point you have
chosen is pointing at the subject from the time you ask it to focus
to the time the shutter opens. With rodeo, that's very difficult.
I loved curves, long before Photoshop appeared