I used to work for a company named Foo Bar Solutions with the public website foobarsol.com, but that used foobar.com for the internal AD name for some reason (which they didn't actually own). That was ... interesting. Microsoft clearly did not do their due diligence in explaining that the domain configured in AD must absolutely, positively, 100% no bullshit, be a real domain name that you actually own and will never relinquish. I'd argue they should have gone so far as WHOISing the domain name in question and failing outright if it didn't exist, and displaying the Registrant/Organization information if it did and prompting "Is this you?" before continuing. Would have saved so many sysadmins so much grief over the years.
And to be clear, Foo Bar is a placeholder here, not the actual name.
I've had to clean a number of these up. The worst is when "foobar.com" answers with a wildcard record. Booting client computers using public DNS in that scenario is like being stuck in a tar pit. The poor helpless operating system tries and tries to reach servers to query for its AD site, find Domain Controllers, apply group policy, run scripts, etc.
Microsoft's official training curriculum for "MCP" and "MCSE" back in '99 was pretty clear about it (I was an instructor at a community college for a Microsoft certification program), but other Microsoft docs and especially third-party docs weren't as clear. Thr whole ".local" debocle with Windows Small Business Server lays at the feet of Microsoft, though.
And to be clear, Foo Bar is a placeholder here, not the actual name.