The simple answer is provenance and blockchain provided this much more than the physical world.
The old world analogy to your scenario is you go to a museum and take a picture of an Ansel Adams work, make a print and try to sell it to Bob. Why would bob pay for this. you have to convince him it's a real Ansel Adams.
Same thing with NFT. You would have to know artist on alpha is real and beta is not. It's non trivial but again I don't think it's actually that different from the real world today. NFT does not attempt to solve this part. Instead it let you check that the nft you're buying is from alpha and the original artist.
I think whether its perfect or not is irrelevant. You can make a high enough quality one that Bob wont know the difference. Same with any traditional art like paintings. Forgeries are not impossible.
The old world analogy to your scenario is you go to a museum and take a picture of an Ansel Adams work, make a print and try to sell it to Bob. Why would bob pay for this. you have to convince him it's a real Ansel Adams.
Same thing with NFT. You would have to know artist on alpha is real and beta is not. It's non trivial but again I don't think it's actually that different from the real world today. NFT does not attempt to solve this part. Instead it let you check that the nft you're buying is from alpha and the original artist.