ICANN has said they will never delegate .internal and it should be used for these kinds of private uses.
I'm a coauthor on this Internet draft so I'm ofc rather biased.
Yeah, not sure why that got approved in the first place. Sure, it wasn't officially part of any of the protected/reserved names or whatever when it got bought, but Google shouldn't have been allowed to purchase it at all since it was in use already for non-public stuff. That they also require HTST just in order to break existing setups is just salt on the wounds.