I’m no expert on screwcutting, Stuart, but I have done a fair amount of it, including internal threads, with the topslide set at an angle of 29 deg. to the side of the cross slide, not the lathe bed. Looking from the front, its handle was pointing at roughly 1 o’clock
Had I set it at 29 deg. to the lathe bed, it would have produced an asymmetric thread, the leading flank of the tool producing the correct angle on the thread flank it was cutting, but the tip of the tool leaving the other flank at far too shallow an angle to the longitudinal axis of the work.
I agree with Bill; it looks wrong, but no doubt John will put us right!
Andy