I researched the state of the art of self-custody cold storage and it seems both complex and fraught with places where workflow accidents could lose a wallet.
Better to lose your digital asset due to your own incompetence than to a hacker of an exchange. Taking the money out of exchanges makes them less appealing targets, too.
You can create multiple backup paper copies, and also 2-of-3 or 2-of-4 multisig helps you in the second case. You can also have multisig between different devices.
You can check the recovery seed that you are creating (what you write on the paper).
Trezor's software and hardware is open source, so you can check any part of it.
There are different things you can do to prepare for different failure scenarios, though not everything is automated, it's better to test some things by hand.
Had you limited your choices to USD / CAD / AUD / HKD (or others in that vein), you may have been making a semi valid point. JPY and BTC are not $ denominated.
So kinda seems like they are cooking the books here.