If you're using a USB hardware token your knowledge of it is at least an order of magnitude better than the median user's. I know where my passkeys are stored, I don't know where my family member's passkeys are stored and neither do they. The same is true for most of my otherwise fairly technical co-workers.
Then that family member does not worry like you do worry. The main point is assuming one can have a proper security for Google account - everything else becomes easy.
The fearmongering of losing google account should stop. Yes, some people lose it. There are a larger proportion losing/getting pwned by repeat use. For the majority - just pressing the fingerprint to access an account (like amazon/eBay) via passkey is great.
Fairly technical co-workers - I used to suggest them to buy USB security key few years ago. Now that same fairly technical some how has at least 2 devices with them - so they just skipped the USB security key need - and just use Google (in Android) or iPhone in Apple ecosystem. Everything just works.
Yes, there will be a poor soul that may lost everything with only one device.
There needs to be industry and government leadership on this to gradually require hardware token usage, for at least critical financial and government applications. Right now everyone is putting their energy behind passkeys, but those are much harder to understand than a physical token. I don’t know any non-technical people who understand how passkeys are normally tied to the device (or the manufacturer-provided cloud account in some cases), how to set them up on a second device, why you might want to do that, etc. And many technical people still don’t get it either!