The TSB and FAA reports are subtly different.
The TSB reports that the aircraft had overflown Twy C for around a quarter of a mile at the point when ATC instructed a GA.
The FAA state that the A320 had passed over all four queuing aircraft before being told to GA.
That may or may not amount to the same thing, although if FR24 is to be believed there was about 0.4 miles between the first and last queuing aircraft at the point where the ACA flew over (UAL1 was just about to turn the corner towards the threshold and UAL1118 was just past the November link).
That aside, given that both reports confirm the A320 was already climbing by the time it overflew the third aircraft in the queue, it's clear that the GA was instigated by the pilot before the ATC instruction was given. That's consistent with the ATC recording:
SFO Tower: "Air Canada, go around."
ACA759: "In the go around. Air Canada 759."