I find some montages to be entertaining. When the clips dance to the music and the "highlights" of a players gameplay are exhibited. I appreciate it for what it is.
As far as "good gameplay", you're correct, montages aren't necessarily a good example of that. There are good gameplay vids out there though. Most of the games shown are usually the up-loaders best or favorite. And that may very well be against trash players that are random with no strategy. But not always.
I do agree that kids should educate themselves on the differences between a montage and a gameplay video. Some exhibit skill and strategy, others are just a collection of highlights.