I installed mine like the first diagram. I assumed the MBC was there to open the wastegate without dealing with the n75. It is a bypass to prevent overboosting even if the n75 does not open.
The second layout seems like the MBC prevents pressure from reaching the n75 until it reaches a certain PSI. the N75 may still remain closed (or open) and I would think you would still see overboosting.
In this particular case he wants the N75 to control boost but for tuning purposes just wants something in place to control max boost.