Nope, not at all.

Yes, but just because the Fusion Dimension was based on GX doesn't mean it has to have everything from it.

Yes, it was a manifestation of the Gentle Darkness… IN GX.

In Arc-V, it’s just another card.

I mean, Super Poly can exist in Arc-V, it’s just that there was a convoluted process of getting the card to exist in GX in the first place.

There is a theory that Supreme King Z-Arc is an incarnation of Darkness/Nightshroud, but there’s only one incarnation of the Gentle Darkness.