Consider this: You only JUST found out about this, whereas a majority of Halo players probably won't ever know about it. What difference will it truly make in the grand scheme of things? And now that you do know it, you really think it'll be that much more effective against competent players who see a jumping Spartan move around the map?
Competent players aren't just sitting in a corner staring only at their radar, so why are you assuming such? They have an eye on it while keeping their eyes on the action around them.
There are a lot of things that the general population won't exploit, but those who seek to understand the games mechanic will. It creates separation. That proverbial "gap" everyone is looking for.
Your argument is that radar hampers movement, is it not? Specifically, Players who see value in staying off the radar typically move less, and they prey on players who move more (and show up on the radar). THAT is how radar hampers movement. Not moving provides an advantage over people who are moving.
However, Due to the mechanics, there ARE ways for players to move freely w/o showing up on radar. Utilizing this swings the advantage towards those who move freely and rely on their awareness INSTEAD of the radar.
On the other side, If your opponent is largely staying off radar AND is able to move efficiently around the map, then your lack of movement no longer provides an advantage. You then have to adapt. The result is both teams moving more, and relying on radar less.
Purely anecdotal, but since testing this out, my flanking has become much more likely to succeed. Too bad I can't shoot for shit, because I've already had numerous multi-kill opportunities but I only end up getting one due to inaccuracy.