rstanarm documentation explains that posterior uncertainty is estimated as an approximation to the posterior standard deviation based on a scaling the MAD (median absolute deviation around the median).

I’m unable to find the scaling factor either in the documentation or in the code. Instead, the SE estimates seem to be based simply on the MAD without any scaling factor (comparing the output of the se() function and applying the mad() function to the simulations).

How the scaling factor for the MAD should be computed?