The reason for bypassing the FDC is to prevent leakage of fuel into the crankcase, an indication that micro particles wear the honed surfaces of the piston within, causing this problem.
It doesn't change any of the abilities of the multifuel engine from burning any mixture of fuels, diesel just gives the highest power output.
If you run on biodiesel/veggie oil, you will notice a loss of power. As a matter of fact, the FDC works in the opposite fashion when using bio-fuels, it reduces the metered intake because it is denser and has a lower BTU rating...
My xm757 features the same multifuel engine but the FDC also has an additional function, which relates to the automatic transmission, it keeps it from overrevving, so bypassing it is not an option.
I have added a magnetic fuel filter to keep microparticles from harming the mechanical interfaces of the FDC and injection pump.
I clean it once a year more or less and it's always a surprise to see how much sticks to it (probably rust from the fuel tank mostly).
Easy to fabricate and highly recommended.
Note: The fuel tanks on this series of trucks were made of aluminum, but I have not found any for my project, so mine are steel types.