apm auth form changes with url

Hi there, I am trying out George Watkins excellent post on 2 factor auth using Google authenticator. It works! This is my first shot at using APM and so I think there may be some tweaks needed and I'm not sure how to address it. The issue is this: If I access the VS with a url (a la FQDN), it works as expected. If I reference the VS by IP address, the APM form changes (omits the Google Auth Token field) and I can fill out the form and it will auth against the back end, and I'm in. This sort of defeats the 2nd factor. What do I need to tweak to shore that up?

Almost forgot, I am running LTM 11.4.1.

Thanks, Mike