Insubordination is simply refusing a proper direct instruction; for example, refusing to turn on your webcam. I'd argue that instruction wasn't "proper". But one of the legitimate grounds for dismissal is refusing to do what you're told. After all, if you hire someone, and they won't do what you pay them to do, then natural justice would seem to say that you can stop paying them, and hire a replacement.

From what I've read, this employee was indeed insubordinate; but they were entitled to be insubordinate, because the instruction they were given wasn't proper. It would be wrong to court-martial a soldier, for example, if they refused an order to murder PoWs, even though prima facie that would be insubordination.