Why were only Ledger devices purchased through the reseller CryptoBilis reportedly tampered with, while devices from other resellers remained unaffected?

If CryptoBilis is a reseller of cold wallets of different varieties then why was Ledger the only one that was tampered with? Could this be that Ledger was the device that could have easily tampered with in comparison to the others OR were they tampered with before CryptoBilis recieved them?