Social engineering applies to pretty much everything. It has nothing to do with Bitcoin (or whatever else a social engineer wants from you) and everything with your own lack of due diligence and gullibility.

I agree entirely - and that is the reason that one shouldn't say "It is perfectly possible to secure a bitcoin one owns."

Semantics. Obviously, theoretically, everybody can be fooled. The common sense definition of secure is not "secure with zero possibility of the security being broken". Storing diamonds in a safe at the bank is secure. Printing your private key and storing it at the bank is not any less secure than storing diamonds there.