Spot on!
This is how I understand the network. And I’m quite sure it’s the way the network works. You are connected over IP to maybe 3 or 4 or 5 IP-addresses. These are relay-nodes. They’ll connect you to a max of 31 nodes in XOR. If you want any data (GET) you request the others in XOR to get it. So you connect to max 31 XOR nodes by using just 3 or 4 IP-connections. This means indeed that there’s always some chatter going on, because all 31 other nodes will talk to you and you back to them as well. And they request chunks from you as well when you are the closes one in the group to a chunk. I laid it out here, and David said it was the way things work indeed. So for this little part (so much I still don’t understand about the technology, it’s so much!) you can ask me to “prove it”. But I ask you to disprove me if I’m wrong 
. Now do you really keep saying that an ISP will see chunks come by from outside looking in? Even while all communication between you and max 31 other nodes goes over 3 or 4 IP-pipes? Here’s another read about how your safe-client goes from IP-level to XOR. Quite some chatter back and forth before that happens. And the different HOPS that are mentioned, before you get a chunk, are in XOR. Nobody and especially someone from the outside can’t make any sense of it. Remember that this is the big trick: your relay-node knows your IP-address but is doesn’t know what you communicate with your 31 friends in XOR. And your 31 friends in XOR know your relay-node’s address in XOR (and some on IP-level) but they don’t have a clue about your IP-address and ports.
I don’t know about the TCP and UDP and all these details. David talks about it in this video. And in some others as well.