Unfortunately, it does matter. FCode still expects to run in 32-bit mode and use 32-bit pointers, so the 64-bit address space doesn't buy us anything.
FCode uses 64-bit pointers on a 64-bit OF. The only thing that's always 32-bit in FCode are the literals (and of course many badly-written FCode drivers do not work properly on 64-bit OF).
Segher