From my tests I'm pretty sure the rear pedal pushes fluid THROUGH the SMC and thus also through to the PCV and ultimately all the way to the rear center piston.
Anyway for anyone here having issues with the rear brake forget about mounting the caliper on the disc like in the pictures in the first post. Just zip tie it to the frame so the caliper is as high up as possible and put something between the pads. I couldn't get all the air out until I did that no matter what. I think I literally bled the entire system a dozen times and had no air coming out anywhere. As soon as I zip tied it up there a bunch of air came out of the middle bleed valve and immediately the pedal was rock solid. I forgot where I read this but I'm pretty sure it was here on this forum that someone posted it so I just wanted to re-post it here in the hope it helps someone. Here's a picture:
