To be fair, I can remember 0 times where as an API consumer I've needed to do different actions depending on whether it was a 401 or a 403 - but I also mainly deal in API->API communication.
I have a production API where sending 401 immediately kills your session and you’re logged out. And 403 doesn’t. We have this as a result of race conditions where the front end incorrectly thinks it still has a valid session. But the back end knows better