The foot brake for the rear is separate. It has its own MC and operates on one side of the caliper stepped piston while the hand brake works on the other side of the piston.
The footbrake is not separate. If you bleed the front brakes and rear needs bleeding or vice versa you won't have any brakes. They push against one another. Like you said the rear pedal pushes on one side of the caliper and the front lever pushes on the other side. Goofy ass system IMO. Yes, if the whole system is operating correctly you can use the rear pedal to lock up the rear wheel and not the front.