What exactly does the custom IP hostname do? It says "send the tracker a custom IP hostname".

Thanks

Normally the tracker will look at where the connection came from to determine your IP address (to send to other peers), if your connection passes through a proxy this is wrong, seeing that the tracker will get the proxy IP address. So this option allows you to tell the tracker that you are really on a different IP address and that it should use that instead of the one it figures out from the connection.

You can also enter hostnames, they will get resolved into IP addresses, before the tracker is contacted;

So if someone slips a TOR IP in there, it is a TOR that is read by the swarm?