Thank you Michael for your explanation.


For my own education, I tried 8 flows with non-Rigid, from the center planar rectangle with the same selection point, to 8 catenary curved surfaces, with the
selection point in an oval. Four came out as "rotations." The other four came out as "rotated mirror reflectons."
Holding a printout up to a mirror shows this as well.

Similarly I tried 8 flows with Rigid selected, and the same selection points. Similarly 4 were "rotations."
The other 4 were "non-mirror," with letters shifted "out of alignment."
EDIT: the shifted letters are corrected by Flip surface normals, so things are more complicated....