Not sure what you mean, I have passkeys enrolled from Apple, Windows and Android devices on my Google account and all trigger the same passkey prompt based on t

Not sure what you mean, I have passkeys enrolled from Apple, Windows and Android devices on my Google account and all trigger the same passkey prompt based on the platform implementation. "Device-bound passkeys that do not support syncing are an option for organizations that require additional proof of provenance of a user’s passkeys". Apple supports what sounds like roaming passkeys but device specific passkeys like you are wanting are already supported by the FIDO spec. I think you're interpreting "no need" here as a if that's a hard requirement. Multiple FIDO hardware keys are already supported on many websites so the idea that the passkey standard mandates a 1:1 relationship doesn't make sense.