This seems like bug or misfeature to me. In my opinion when new
users reach your site they should be redirected to your actual
login page instead of showing Tender's login page with only a link
to yours. I think the original purpose was to allow users with
non-SSO accounts to log in, but this can be worked around by going
directly to /login on your Tender.
I've made a ticket to fix this, we'll let you know here when