It's similar to how gifwraps work. The forwarding relay knows your IP (because you connected to it) AND knows to which server to send your message to. So, if you are talking to somebody for a while, the server has mapped your encryption key + IP + location with the "next hop", which they forced to be the final hop. It knows how many messages where sent, and when, to that specific destination. If you are following their guides and using a different server for each receiver, then the forwarding server can map out how many different people you are talking to. 

Ideally, these forwarding servers should be randomized per message so that they can't assemble a conversation, and if the app can add more hops, it becomes even better. 

It's kinda where we are going with NIP-17, using random DVMs to forward content to the next relay/DVM. The starting IP is obfuscated by randomness. 

But in order to do so, the community must have 1000s of forwarding relays out there so that the app can randomize them per message. 

 IP obfuscation is a separate problem. Always has been. The shop down the road doesn't care how you get to the shop either, it's not their problem.