Passkeys are a multi-vendor standard. Because Windows is no one's phone vendor today, it's generally a good idea that Windows has strong Passkey support because

Passkeys are a multi-vendor standard. Because Windows is no one's phone vendor today, it's generally a good idea that Windows has strong Passkey support because it can be an intermediate between the two major phone vendors and help even average users avoid vendor lock-in by pushing a majority of users to try keeping keys with at least two vendors (their phone, and their Windows device) in their common accounts.