There aren't the same effect.
There is a semantic difference, and only that. You're presupposing that one affects the monster and the other affects PCs, but it might actually be that one was designed by one guy who writes powers in one way, and the other by another. One might have been written before they started using the concept of adding tags like "watched" to powers, which only came in later.
They might actually be the _same power_, in different sources (ex: Printed vs. Compendium)
Would a monster know of a ranger's Disruptive Strike power before he uses it?
Nope.
They certainly don't support automatic knowledge of what a power does to others either
The rules don't support your distinction. A target provoking OAs when it attacks being "on others" because they get to make an OA vs the target, cause he provokes, isn't defined in the rules. It's a construct you've created to explain a distinction, and if it were in the rules, that'd be fine.
But it isn't.
The only guidance I've ever seen and the only play I've ever seen, is that when a power is used, you explain its effects (and "the target is going to get hit if it attacks" counts, no matter how the wording is manipulated), and folks react accordingly. It's the consistent way to follow the "monster knows what you did to it" rule and it works well in play.
But for the various reasons previously discussed (in short, RAW and powers that don't work otherwise)
What powers don't work?
Dance of Death works great for shutting down further attacks against the rogue, and has extra synergy with attack redirection or target forcing powers.
Riposte Strike and Brash Assault create a very real choice / catch 22.
You're suggesting that the rule is vague and difficult to execute. Well, (A) it's D&D, there's a DM for a reason, use common sense.
D&D has rule arguments over simpler stuff, indeed. People just like arguing

I wouldn't use the words "common sense" with respect to D&D though... that way leads madness.