I just found another possible explanation:
"There is a solution: parent and child.
Make your SKUs a variation of a parent item. Parent item will have different SKU for each market, but child items can have same SKU and sync across markets.
This way your main images can be different for every marketplace, as you are not selling the actual parent. In my case I have only one image for child SKU and it is synced across markets, but it is only shown in some places, like PPC on competitors listing (auto campaign).
Keep in mind, that how images work depends on the type of variation you choose. I believe it has to be a variation which does not have to be visualized. Color will not work, for example. Pick something like shape or type of handle or something of that kind."
Can this be the case?