A friend of mine managed to be fired after he achieved FI, after he sorted more or less everything for the future he was just as you describe, by his own account he was “totally unhinged, not tolerating anyone or anything”, so they booted him with a note next to his name “never interact with again”.
Funnily, he says he managed to get in such an argument with his bank, to the point where they handed £20,000 to him in cash, and a cheque for the rest of the money and told him to fuck off and never show up again in any branch or he’d be arrested on the spot. True story (no, really - I said “quit” in my linked story but the reality is he got fired, even showed me the emails).
Edit: it’s a sad story in its core, underscored by severe trauma and mental health issues, FU money is critical (even my old boss told me “I have FTS money” - you can deduce what it means) but keeping up propriety is not only a formality in my opinion, but good functioning too.