If you are going to tell that may confuse users, I think not having a password field is already confusing the other half, while also not being password-manager-friendly.
The current trend to only show the password box after the username is provided doesn't have to be bad for password managers. I use loads of sites that do this (so they can support SSO) and they just use hidden form fields so the password managers know what to do.
I'd be curious to hear any suggestions you have for password managers to improve here though. I can't think of anything short of a .well-defined login route.
> Using Single Sign-on (SSO)? Simply enter your company email address and click sign in.
Seems simple enough to me as a user, not sure how most people interact with it though or how many companies A/B test these things.
(Just don't forget to donate, if you have the means.)