The intention is this is all driven by control loops, which yes should run synchronously, but I haven't
provided all those levels, its just test code for driving the PWM stuff.
Yes you could wrap u, v, w updates in noInterrupts()/interrupts(), in practice you'll very rarely see then
updated late (depends how fast your motor spins reletive to PWM frequency if this is significant - for
instance if you are Celeroton driving a 500,000rpm brushless motor this matters a great deal, but at
4000rpm and 16kHz PWM its no a big deal).