I think this is a bug. In pandas I saw what you said, it takes out categorical columns, but it used the rest of columns, mainly float64 and int64.
Instead with plotly if I try to plot the boxplot of A, B it works, if I try to px.box(aux.iloc[:,:3]) it returns again “ValueError: Plotly Express cannot process wide-form data with columns of different type.”. And okay, is true that there are different types, but in pandas works, and here I suppose it should work too since both are numeric types.
I used the data from the first post, being A&B float64, and C int64.