The right/left balance and power phase was discussed in a podcast a while back. The focus, I recall, wasn’t on Garmin’s data as much as CompuTrainer’s power graph and that TR could (or does) capture this data but found it unnecessary. The drills will help even out the pedaling (in)efficiencies and putting the info on the screen would be a distraction from the focus on targeted power output. They also discussed, I recall, how we aren’t machines and the perfect circles did not conform to real-life applications, including pros, so they opted not to capture or display that info.
However, as noted, your power meter captures that so you may review it outside of TR.