I'm sorry, I have never seen your "reverse" method mentioned anywhere, let alone recommended as the proper way to bleed a brake system.
by pumping the fluid backwards through the system, you would carry any contaminants back through the RABS valve, any other antiskid or traction control devices and combination valve that may be in the system.
A recipe for a major malfuction if not disaster.
That is the reason to open the bleeder to vent brake fluid when collapsing caliper pistons instead of backing it up to the master cylinder.

 

This method is used by many for bleeding motorcycle brakes. It's used because it can be very difficult to get an air bubble to move down the brakeline to the caliper on a motorcycle, especially a Harley with DOT5. On my Harley I don't bother using the pump. After bleeding, if there is still air in the system I briskly push the caliper piston back in. That will usually take care of the problem. Some people do use a pump.

I have seen some very cruddy master cylinders so I think the crud could come from either end.

 

there is not contaminants that are not already in there, ther is not large particles int the caliper piston bore that might migrate to the master cilynder.....

mr fsc; backwards brake flushing/bleeding is the only approved method by the a.s.e. and by a.m.a. and a.s.a and the u.s. navy and the u.s. airforce,