First I've heard of it, but I'm not a grip or gaffer or anything. More compact seems nice. But more small parts to keep track of? And not free. I have plenty of grip stuff for my small jobs. I'll ask my fav gaffers et al as I bump into them (not much work planned for the next 1.5 weeks, of course).
Never seen that on a real set. Matthews makes a lot of silly stuff that doesn't catch on and then quietly disappears, I suspect this will do the same - I've never ever heard anybody express a desire for an interchangeable baby plate.