So potentially by having the brakes on the same side then the vibrati8ns could cancel eachother. I’mnot convinceda bike is a linear system, I also think the chances of the brake input at both ends being equal at any time during a ride are so low that it probably makes no difference. Good practice to think like this though, and chapaeu to andyl for raising it.
/pedant
Alternatively, in a complex situation you may have resonant effects and create all sorts of adverse goings on.
the primary reason for having discs on one side is that that is what we have & the mass market don’t like to be challenged with differences. I don’t believe that there is any significant difference, especially for a post-mount.