Earlier quoted context omitted.
Seems an appropriate word... "Insubordination is the act of willfully disobeying a lawful order of one's superior." Your boss is your superior, so disobeying what he asks of you is insubordination.
You seem to have missed the word "lawful".
If I tell you to go buy 10 apples, refusing would be insubordination because it's legal to buy apples.
If I tell you to go steal 10 apples, refusing would not be insubordination because it's legal to buy apples.
Until the court ruled against them, the view of the firm would have been it was legal to require someone to have their camera on. Hence they viewed it as insubordination to refuse.
They are wrong, it's not insubordination, but it's not unfair of them to think it was.