I"ve debated this before but there is still a difference in BLD programming between the FD1 and FDII vehicles, the bit difference is the pressure which is exerted on the wheel spinning.
I have even recreated this with my FDII because it functions exactly like a FDI when not in the FDII specific mode.
You can tell when the FDII mode is active because it actually completely stops the wheels in the air from spinning and provides movement. A FDI does not do this and even if it had the same BLD programming the lower "crawl ratio" doesn't give it enough torque to provide meaningful movement
None of the 3 FDI's I wheeled with could do this obstacle
The point i'm trying to make is there is difference which you can't ignore the FDI does fine, but all things equal the BLD programming on a FDII is entirely different which allows it to navigate obstacles when there is lots of articulation I did this for 8 years I know what they can do. I'm not taking away what your vehicle or anyone else' can or can't do but i'm stating the facts
For 99% of people they probably don't need FDII but there is a difference and they are different offroad