Regarding the components of hardware wallets being obscure, such as the HSM and the Secure Element available in HW such as Ledger, it's difficult to trust completely, since these parts have an NDA agreement that these manufacturers that sell HW are obliged to comply with. i.e at the moment we don't have open source SE, but according to Trezor, this will be possible in the future as they are working on it.
I don't fully trust HW, but I know that at the moment they are the best options for beginners who don't understand anything about air-gapped storing coins safely.
I think this deserves a topic just for these hardware wallet dilemmas (if we don't have one), so I'll return to the subject of this thread.
All that isn't an argument against BIP39 seeds. His paranoia level is at a point where he believes his coins will be lost because someone out there will find them and empty his wallets. To be honest, I don't think it's healthy.
Agree, worrying too much about one thing and ignoring another is not a good thing, as it opens the door to online vulnerabilities.
When we are on the subject of paranoia, why is he only afraid of someone finding his physical backups? Why not be afraid of someone very knowledgeable getting physical access to your computer? Sure, they would have to break all the encryption, but still. Or even worse, why wouldn't that someone tie him up and torture him until he gives them what they want? At that point, it doesn't really matter what you used for your backups.
One of the best ways to protect your coins is really not to tell anyone that you have bitcoin, at least not unnecessarily, you can take every precaution to protect your wallets and backups, but not take care of privacy and go around telling friends that have bitcoin and making a lot of profit from is a decoy for physical attacks such as the wrench scam. Of course, most people you talk to with Bitcoin won't do this, but I feel uncomfortable when close family members ask me how much Bitcoin I have or tell others that I have it, as if I own a large amount, rather than to discuss the fundamentals and potential of bitcoin as a tool to improve our lives as well as protection against inflation and privacy against crooks and governments.
Whenever they start asking personal questions, I tend to deviate from the subject, as one of my mistakes was having said too much in an attempt to show what bitcoin is and how it works.