Whoops, looks like the tab and the backing track ended up counted differently!
The pickup notes I was referring to are on beats 3 and 4 in the tab, and the implied beat 4 in the backing track. Each metronome click in the backing track was regarded as a quarter note, but to play in time with the backing track, “quarter notes” in the tab have to be counted as “eighth notes” when played along with the backing track.
This is all based off counting that faster “1-2-3” as quarter notes (because it is implied there are four of those beats in a measure).
This doesn’t affect the actual speed of the song, but it can get confusing when one musician counts beats a different way than another. Apologies for the confusion!