If you use the lever on the footrest with a linkage to the gearbox, the direction of change is maintained. My TTI box came with a Triumph shift pattern, i.e. one down and the rest up.. Being a dickhead I just fitted the box and when I tried to ride the bike, it would not move. So I gave it a heap of revs and dropped the clutch. The Commando has so much torque that if you rev it, it will pull any gear. The bike took off in 5th and I almost stuck it through a fence. It had a fair distance to run, and I caught it in time - just !
I think that lever and linkage is standard on most Manx Nortons. I think Bruce simply fits the change drums which he has the most of in stock at the time.