This count as air gapped device but why not just invest on a hardwaware that is 100% air gapped like Keystone and Elipal instead of relying on an old PC that has the tendency of being not functional in future? You will need to import your seed phrase once your computer broke so why not invest earlier on much reliable air gapped wallet.
If you buy a hardware wallet, there is also tendency that the wallet can be damaged at anytime. He has an old computer that is not useful, I do not see anything bad if he make it useful by turning it to an airgapped wallet and install bitcoin wallet on it.