They were saying what it meant in this context

Meaning, in a DB, the admin could change roles and modify anything.

Database triggers can have bugs, and we generally don't let third parties log into the database directly because it's a huge attack surface

In blockchain, without a key you're cryptographically locked out. The only way around that is if the network as a whole changes their code to a version that allows something like that

It's just a ledger where every entry is signed by a private key. That's a fantastic structure for certain specific use cases...