The purpose of opening the front bleeder is to get the system to think there's a leak and move the pressure differential valve so the rears with the height sensing valve can be bled correctly. That's why after the initial rear bleed with a front open, the front is closed and the system is bled again.
I had a similar issue, I rebuilt the MC (yes old school) and all was good.
From '92 FSM: It also says not to pump brakes, just depress pedal.