please take a look, they are not using voltage boost, they are using motor timing boost (adjust the phase timing of your motor by using electronic pluse). If you set the timing loop too much, the induce current will flow back, and need your esc output FET to handle, this is the reason the ESC will having a reversed loading all the time. Below is the staement from their website.
TEAM WAVE raised the bar to the next level by introducing the "Time Shift" technology