POE 1 MTX unavailable, even tho the same MTX gets sold in POE2

Hi guys.
Back in the days, I've bought the Cordyceps Bow skin. When I hover over it at cosmetics, it tells me that the MTX is not supported in this game version.

However, if I go into the shop and weapon skins, exactly that MTX gets sold. So it means it has PoE2 support. Is there any reasonable explaination for that?

MTX: Cordyceps Bow

Char: TanzendesBaerchen