A sensored ESC with a sensored motor DOES know what position the motor's timing is in, & as such, it DOES matter how the motor itself is timed. It's been awhile since I've used boost on my ESC's(the motors around when I did had more limited mechanical timing), but I noticed that some types & brands were more tolerant of boost than others. For example, when I started using boost, I had mainly Novak Ballistic series motors, & noticed that they HATED boost, made no difference what the mechanical timing was set to, they still overheat no matter what I tried(even when intentionally undergearing them, & then they'd be both slow & run hot). but we also discovered that Trinity's Duo2(D2) series motors appeared to be MUCH more tolerant, & we could use timing advance both on the can & in the ESC(though I believe we usually stayed at about 20 degrees advance on the motor itself), & would shoot for somewhere around 50 degrees combined timing(& use the ESC settings to adjust where & when the ESC boost would kick in). But it's generally diffrent for every different design of motor, so it'll really come down to a lot of trial & error for you in figuring out how much to use on the motor & how much in the ESC(best to start maybe with 20 degrees on the motor & gradually experiment with the ESC, adding a little at a time)....