I am awfully sorry for annoying but i just want to understand it right...
is this clearly not possible?!?! i am sure i got this working on my old omv 5
trapexit (author of mergerfs) would have to explain how that works more. I would guess it is trying to keep "SomeFolder" together.
I don't know why it would work on omv 5.x and not 6.x because the mergerfs is exactly the same. The plugin just puts the policy in the options. mergerfs does everything else.