If twitter fraudulently verified something there is absolutely something you could do - you could sue. And it would be pretty clear cut.

And all you can do on Mastodon is moderate your server - they can still be out there in the greater Mastodon community and there is even less you can do about that than you have recourse with Twitter.

All this sudden pearl clutching sure is amusing.

Meanwhile before the acquisition, on Twitter, someone could sign up and pretend to be a member of your organization and... there was still very little you could do about it. Verified checkmark is a red herring, because it's not something you could guarantee for yourself or other members of your org. You were better off - and still are - with something like Keybase, or... well just not using Twitter for anything important in the first place.