I'm going to go out on a limb and say that Colemak wasn't designed specifically for high-quality keyboards. Your shift usage is hardly different between Colemak and QWERTY.
Is QWERTY's shift usage already optimal or did Colemak just not improve it much? There are many things to optimize when it comes to shift usage. For one thing, the left shift is way easier than the right. Some letters are more likely to be capitalized than others and ideally you want to minimize using that same pinky again--a "hidden" same finger to look out for. Ideally you don't want to even use the same hand that used the shift until hitting a couple keys from the other side. For instance if you have to do a right side capital letter (left pinky) then the letter following it should be something on that same hand, but not awkward, not the same finger, etc. Shift can be optimized a great deal but it's not that frequent so it's not really a priority.