Passkeys on tiaa.org

I have an account with TIAA (tiaa.org), a non-email username, a password, and a passkey.  I'd like to use the passkey to log in instead of my password, which requires a 2FA message to my phone.  But I haven't been able to get autofill to successfully apply (or offer to apply) my passkey.  I'm using the Safari browser in macOS 26.5.1.

With both my password and passkey included in 1Password, if I click in the User ID blank and click the pop-up OR if I type cmd-\, 1Password fills in my username and password, sending me to the page to request a security code.

If I remove the password from my 1Password entry (thinking that this will force the use of the passkey), 1P fills in my username and then I get an error "Your login information was not correct.  Please try again."  I think 1P is still clicking the "Log in with password" button, rather than the "Log in with passkey" button.

The only was I've been able to log in successfully with my passkey is to manually fill in my username, click "Log in with passkey", and then clicking the passkey Sign In button in the 1P pop-up, though sometimes this takes several attempts.  Sometimes the browser shows a window saying I have no passkeys for this website, even though the 1P pop-up is already offering a Sign In button using the passkey.

This makes me think I'm doing it wrong.  🥸  But it sure seems like 1Password is not detecting that TIAA works with passkeys, or maybe TIAA has something configured weird.  Is there any way to make this login work smoothly using a passkey?