what is the benefit or in which situations would someone call clean()? If user wants to disconnect client, they can just call client.disconnect() and it would call the clean() method internally. That would be much more cleaner right? does is has something to do with who closes the network connection first?

This is to solve for the problem that we might end up dealing with when eventloop is blocked on handling inflight because of bad network and that is leading to us not being able to disconnect as the request waits for the channel to recv. So just a fail-safe to ensure we can save pending packets onto disk and they aren't lost because of the possible situation I have mentioned.