That is how it was explained to me by a person that builds brushless ESCs for a living. I made the mistake of calling it "three phase AC" one too many times, and was sternly reprimanded...

Anyway, we may be looking at this in different contexts. The voltage flowing through the motor may be "alternating," switching direction, but it's not AC as you'd see out of your power lines. There's no gradual ramp-up to full voltage; it's ON or it's OFF...

What you seem to be describing is the behaviour of the electricity at the motor. I'm describing the "mechanics" of the ESC.