It depends on the companies and producers of collectible coins. If they are not trusted and did set up some thing for scam exit, to claim your private keys later, it's not completely safe.

If any founder of collectible coins do things like Yog, it's surely not safe for any buyers and collectors.

No record of the coin being compromised but I do not trust collectibles generally.

The people that created the coin have knowledge of the private key.

Those loaded with Bitcoin? Depends on where you bought your physical crypto and its to risky to trust those people offering this so pick those reputable people selling this coins to avoid getting compromise.

But for you and other people to be aware on past incident physical scam coin hacking @krogothmanhattan had a thread compiling those incident here https://bitcointalk.org/index.php?topic=3315347.0

For sure you will get interested to read those cases and to know the risk of what you are trying to buy.

 Yes, the creator would know the key if they put it there. When you buy such a coin youd be trusting them completely not to steal the funds. If you want a physical representation, buy an empty one.