I'm sure rev matching helps during a roll, but how about from a stop.
Occasionaly (usually when people are in the car so they can laugh at me) at a dead stop with the clutch ALLLLL the way down I try to shift into first and GRIND.
Took it to a dealer, does it less but still does it.
I don't even think the syncros are involved at a stop the input and output shafts should both be at 0.
I'm waiting for someone else with some free time to bug there dealer and get his fixed.