Hello - In 473, choosing 'Sign in to this account' from the context menu of a login item takes you to the 1P account sign-in dialog, where it does enter the login item values. I would expect it should open the default browser, go to the website and automatically enter credentials.
It's a little confusing from the release notes where it says "If you have other 1Password accounts saved as Login items in your 1Password database, you can now right-click on them to sign in quickly if you haven't done so." That would indicate the context menu option is only for 1Password account login entries? It would explain the current behavior, but I'm guessing it shouldn't have broken normal login item functionality.
1Password Version: 6.8.473
Extension Version: n/a
OS Version: Win10 17025
Sync Type: All