I am still trying to figure out my own code, but I made the change based on my sophisticated "fling the track" test.  Take two tracks, one master, one slave.  With the mouse, grab the master track and fling it as hard as possible.  With the AFTER processing, the tracks would get out of sync (and then recover, thanks to syncadjustment).  With BEFORE processing, the tracks would be in sync for the entirety of the fling.  Note that that test is independent of userTweakingSync (no buttons, wheel, or jog used).