This is not true, there are sometimes exploits that can be used or manipulations through the software to trick the user. It is better to do things with clean devices. You save little money for a lot of added risk. Why not avoid this if you can?
Sure. That's probably a good idea as well, but IMO it gives a false sense of security to the user as well. Refurbished wallets with OS wiped is safe as well, in fact, if you're buying a new laptop, you should also wipe the OS. Spyware and bloatwares are common with the new laptops.
There should be a few key principles that are reiterated to the users for most of the HW wallet users.
- Not exposing your seeds to third parties, or devices.
- Checking the addresses and amount thoroughly to ensure that the amount that is being sent and the address is correct.
For reputable HW wallet manufacturers, these are sufficient. Exploits are rare, especially software-based exploits because of how the HW wallets communicate with the computer. Social engineering is far more common in comparison.