My opinion is MUP is more analogous to sidewalk than street. Pedestrians should have reasonable expectation they won't be taken out by fast moving vehicle. While I have yet to see a direct hit, I've seen numerous near hits to a degree if I were the pedestrian I would think twice about coming back. Particularly among the very young and elderly. Cyclists are constantly taking high speed risks painting the yellow line between groups in opposing directions, rather than waiting for proper opening. I think parents should make a concerted effort to teach awareness, but kids occasionally stray, that what kids do. Parents shouldn't need to worry they're endangering their kids by talking a walk on a nice trail; or helping to instill confidence with the training wheels off their own bikes.

And to the primary point of OP yes I've seen pace lines flying down the MUP...