Olivier et al.
I spoke too fast. "PPL txlabp, 1" does move the labels to the right but the labels overlap with the axis.
However, even if the axis is on the right like requested, the result is pretty bad on my plot :-((
(with PyFerret v7.63)
I get the same result as you. PyFerret v7.6, v7.6, and v7.5 on macOS, Linux, and Linux, respectively.
Ryo