I think this is a thing of chance... with one exception:
A gnutella-client behind a firewall often can reach the network only by outgoing connections.

So if all of your connections are to firewalled clients of this kind, all your connections are incoming.

For sure, some Firewalls have an open port for gnutella. Then the client behind can be reached by incoming connections. But many firewalls are not opened for gnutella!