Don't you think an excuse could be fashioned that some officer (mistakenly) believed that he was acting in accordance with the requirement to get a warrant, even though he hadn't?Yes. That's exactly why there are so many IQ<93 cops out there....
We don’t have any idea how this would have turned out if permission had been refused. The ruling doesn’t apply to such cases, although state attorneys will attempt to argue that it does (always try to stretch the law, maybe you’ll be lucky).