Your answer is totally reasonable, but I admit I don't have time for that in most cases.
1. Most services are not Passkey-only--most people are using it as a password alternative (e.g. eBay) or a second-factor alternative. So losing it won't lock me out.
2. A very small number (e.g. Google) let you configure Passkey as your sole second factor. For those, I am indeed careful to do what you do and have duplicates.
I do think this is kind of bad? So the grandparent totally has a point here: services find it hard to do only Passkeys (and thus realize the security benefits).
But, as a user, it's not something I worry about a lot, to be honest.
1. Most services are not Passkey-only--most people are using it as a password alternative (e.g. eBay) or a second-factor alternative. So losing it won't lock me out.
2. A very small number (e.g. Google) let you configure Passkey as your sole second factor. For those, I am indeed careful to do what you do and have duplicates.
I do think this is kind of bad? So the grandparent totally has a point here: services find it hard to do only Passkeys (and thus realize the security benefits).
But, as a user, it's not something I worry about a lot, to be honest.