As they said --air-gapped smartphones are much safer than the air-gapped PC which are vulnerable to hacking, did you know that even fully air-gapped PC can exfiltrate information through the output radio signals generated by the computer or call ^{[electromagnetism]}.
Also expert says that through ^{[ultrasonic waves]} a virus can be used to steal the private key out of the computer.
I had always preferred the hardware wallet over the old PC or phone for cold storage, they don't have the security features that hardware wallets have. A hardware wallet has minimal attack surfaces not unless they steal it from you personally.
So no way for the old phone to be a cold storage wallet or worst a PC to be a cold storage wallet, however --I am overthinking for 25% way of a possible scam using an air-gapped wallet.