Yes, this is right. It only recently dawned on me that the tracks sent into the FX are effectively a sub mix, so the levels for those tracks are relative to one another inside the fx block, whose volume can be adjusted relative to the master mix.
I realized this is useful because the analog drive depends on the level of signal going into it, to achieve distortion on 1 or 2 tracks only, you have to max out the level going in (and usually adding track overdrive helps too)… those tracks can be mixed relative to one another, and then the fx block can be turned down a bit to go with the rest of the mix.