The only issue is, these cars are without documentation.
You only receive a registration book. And these cars can be a pain in the back when selling.
If you are naive a car dealer can sell you such a car for market price and then you have to sell it at loss. Such cars have lesser market value due to non availability of documents.
Altho they are completely legal and the book is stamped "custom auctioned"
The issue with cars not registering came up in amnesty scheme cars. Custom auctioned cars are no problem.