Yeah this has become a problem when using aftermarket master cylinders. Mopar had the front ports feeding the rear brakes for years but the aftermarket decided that was confusing so they switched over to having the front port feed the front brakes. The master cylinders al look the same and often there is not any instructions.

My buddy at the chassis shop says he has to bench bleed each master cylinder before he knows how the car should be plumbed. It used to be easy but now it is kind of a crap shoot about how things should be installed.