But do dovetail clamps really make sense on the Workmate?
The jaws of the Workmate are practically an ideal clamping surface for the professional-grade clamps that most of us already have. There is full access to the top and bottom surface. The jaws are narrow enough that standard-reach clamps can reach to the middle of the jaw from either of its sides. So with standard clamps you can choose almost any spot anywhere on the jaws to clamp to. As I mentioned already, the dovetail clamps can't do that. And there's no need to rout your top and buy new clamps.
When I look at Microjig's site, every illustration of the use of their dovetail clamps is either 1) in the center of a large work surface, or 2) on a surface where there is no access to the lower side. Of course they're a great option for those situations.
But how often does either of those things happen when clamping to a Workmate? Your example photos could certainly be handled with standard clamps.
I do see one advantage to the dovetail clamps, an advantage shared with the Gripmate -- you can loosen them and they will stay in place until you tighten them again. With a standard clamp, you may have to remove it completely and set it somewhere.
On the other hand, I also understand why someone who already has the dovetail clamps (presumably because they have one of the tricky situations I mention above) would be looking at every other surface in the shop to see where they could put another groove!