If you want to make sure that your Bitcoins don't get lost, you need to create a full backup of your wallet with your Bitcoin private keys. In addition, you'll need to create a hard copy of them somewhere that you are sure not to lose. But, the most important thing is to avoid your private keys getting into the wrong hands in the first place.
Never mind, wallets are now generating seed phrase, should we still be using private key backup? Whenever I read private key backup, I still always think seed phrase is better. But OP is not wrong at all, there can be some hackers that might demand for private key from people, be it seed phrase, seed, master private key or private key to a single address, people must protect it because it can be used to steal coins, only what should be given to someone or people should only be the bitcoin address.
You shared two opinions about the Privacy of Crypto assets. We really need to save our private keys far away from online because when it will be shared to someone or be havked you guys lose whole assets. So make sure your private keys are secured.
If you protect your private key, is for the security and safety of your coins, not for privacy. To have privacy, you will have to run your own full node wallet with Tor. But you are right, for your coin not to be stolen, the private key or the seed phrase has to be protected.