Tech-savvy keyboard users wouldn’t have an issue. But some disabled users relying on screen readers need to use a keyboard, and are not all tech-savvy.
Those users might still search for a login button to submit the form and not rely on submission from the password input field. I think making sure the login button is not too far away from the main content of the form would help non-tech-savvy keyboard users a lot.
@MichaelHamann left a comment on this subject on the PR here.