No. In blockchain.com wallet"non-spendable " means that he imported just the public keys of that address.
Blockchain.com allows you to track addresses balances using just public keys , and call those addresses non-spendable.
He probably doesn't have the privatekeys, unfortunately. Or if he has he didn't imported it into the blockchain.com wallet.
You are right that the OP may be a victim of a scam where the attacker gets the victim to add his addresses as watch-only to a bc.i wallet. However addresses are not public keys. Please use the correct terms or we get questions like these.
cash just for that balance and since OP didnt answer nor visit again this page theres still no clarification but most likely these cases are common.