When using a bend in the thumb as a grip, I have found that sometimes I could find a grip that was allowing me better control of the plectrum than was typically the case.
And now I think I know why, and I’d like to know if anyone else has found this.
If I grip at the centre of the plectrum, I think that allows the slant, the vertical symmetry, to be altered with a tiny amount of thumb squeeze taking the pressure of the grip either below or above that centre, and that gives me a grip where I feel the slant is much easier to control.
If this is the case, perhaps this is how those players who use bends in their thumb can alter the path of the escape with a movement so tiny that unless you looked for it you would not know it could happen.