I imported my collection from Curiosa, and when I add cards to a deck, the overlay still says I "own" 0 and "need" however many I've added to my deck. When I download my collection, it appears that each card has two distinct representations, with different "variant slugs". (See below.) It appears that the slugs with leading numbers ("006") are what the overlay detects, but not the ones with leading short codes ("got"). Given that there appears to be no other distinction between the cards, there should not be different stubs. (In fact, are stubs even necessary?) The one imported from Curiosa all appear to have been assigned the short code stubs.
In the collection card screen, you can also see this unnecessary duplication, if you expand the "In Collection" button to see the specific variants.
"card name",set,finish,product,"variant slug",quantity,notes
"Archangel Gabriel",Gothic,Standard,Booster,006-archangel_gabriel-b-s,1,
"Archangel Gabriel",Gothic,Standard,Booster,got-archangel_gabriel-b-s,2,
"Archangel Gabriel",Gothic,Foil,Booster,006-archangel_gabriel-b-f,3,
"Archangel Gabriel",Gothic,Foil,Booster,got-archangel_gabriel-b-f,4,