What About Watergate?

I was traveling yesterday and unable to listen to the oral argument in the Trump immunity case. I've only read the transcript. But I don't understand how the Court's thinking can be squared with Nixon's alleged crimes during Watergate. Many of his actions there were official. Indeed, much of the problem was that he abused his official powers (for example, by ordering the CIA to cover up the burglary).

I take it that the Court believes that Nixon could have been prosecuted after he resigned. Is the answer, then, that his actions during Watergate will be recharacterized as unofficial? If so, that comes close to making real the joke in a "Yes, Prime Minister" episode where an action is described as "unofficially official but officially unofficial."