I see we're kind of beating around the same bush with slightly different viewpoints.
You say that lowering the tail rotor shortens its arm about the CofG compared to that of the main rotor side force, therefore reducing its effectiveness as a rolling agent - result, more left roll.
I say that lowering the tail rotor increases the arm of the MR side force / TR side force couple, increasing its power and ... creating more left roll.
From the hover, if we level the disc and let the aircraft drift, the left side force from the head goes away. Because the couple mentioned above no longer exists (no MR side force), the body is now free to hang so the CofG is under the head - it's now rolled right compared to how it was in the hover.
As it drifts, drag will come into play, and a rolling couple will be set up, the direction of which will depend on the relative vertical positions of the centre of pressure and the tail rotor side force.
Applying left cyclic to stop restores the original couples, rolling it left again compared to how it was in the drifting state.