It seems like it is acting like a master FX loop in/out for the octave and Big Muff. So they can be switched in and out of the signal chain, whereas the TU-2 acts as a master mute for everything.
So, not really redundant, in my view.
Give the man a cigar. I'm using the 'master switch' part of it to keep the effects out of the signal chain when they are not in use. At some point I may spring for a fancier loop solution as there are so many cool options now. Same with the tuner and cables. I basically just pulled together stuff I had laying around to get back in the pedalboard game.
Are you running the octave and fuzz together at the same time, one foot press rather than two?
The reason I asked is I'd figure the buffer in the PSM-5 is of lower quality than what's in the MXR and Big Muff. Effectly taking two non problematic pedals out of the chain just for good measure, while dropping in a potentially problematic pedal instead.
If you haven't already done so, I'd suggest setting up your rig in a listening environment and trying it both ways to see how it sounds. You may find you can remove a pedal and gain more room to replace it with something else.