The player in this gif is clearly dependent on motion tracker. Well, how so you may ask? Because he throws grenades without first being aware of his surroundings due to that little red dot he must eliminate, despite his teammate being right there. In this same video, you can see how many times they dance in circles because the players know where each other are, leaving less room for interesting plays.
It happens all the time. All. The. Time.
It's important to reiterate that
motion tracker is the problem, not
radar. You can have a radar for matchmaking similar to CoD's where it's only based on sound (meaning when you fire, you appear on the radar, not for movement). Sound-based radar is the best compromise for Halo Matchmaking IMO.