Safari prompting for local user account password on Apple websites
This is a new feature with safari on macOS and Catalina when you are signed in to your iCloud / AppleID on trusted and keychain synchronized devices when communicating to some Apple secure services online.
Your local admin password unlocks they key store and sends a secure token rather than your iCloud password to authenticate you through Safari to Apple’s web site.
Ways to opt out:
- Sign out of iCloud on that Mac.
- Use a different browser.