Calling fastcgi_finish_request in post_system event handler

Suppose I have an API returning a JSON-serialized object to a client. Can I use fastcgi_finish_request() in an After filter if I know, based on the route, that there is no more data that would be sent to the client?

I'm just not sure what is happening behind the scenes which I might end up breaking by using fastcgi_finish_request() in abnormal places.