The problem with physical crypto cold wallets is the verification of authenticity. Since there is or was no standards, buyers are always left with proving that buying a cold wallet is
- still loaded - yes can check the visible public key
- private key is not compromised - only possible if buyer redeems the coin immediately (best in front of the seller) to confirm that they do get the coin.
Every moment that lapses between the verification of the public key and the redemption of the funds from this wallet increases potential risk.
These particular coins may be less so because buyers may be able to verify the surface integrity of the coin and packaging against other examples in the wild (assuming they are also not copies)
But anyone aiming to make a biz out of creating, loading and selling cold offline wallet formats eventually has to wrestle this fact.
Producing true verifiably virgin private keys - the ones that not only are internet virgins, but also have never been copied somehow during production, is exceedingly hard to do.
It's not impossible to counterfeit these Casascius holograms (in fact, there is evidence that someone did so at least once), but any prospective buyer can look up the address on the coin via Uberbills to see that it's still loaded, since all are on the blockchain. Most of them are sold via the same sites and if the same BTC address were to appear in repeated sales, it might raise a red flag.