The ppc plot does not use the mu variable but the likelihood one, which is the one that can be compared to the observations. And likelihood has no information about any dimensions or coordinates, so it can’t know which observations correspond to which gender.
This is also what happens in the radon example in plot_ppc docstring. We need to assign the coordinate values of what we want before calling plot_ppc. You’ll have to follow the same steps, but the obs_county won’t be an array with the county that correspond to each observation but the genders of each observation, in your case I think cat.categories