So erlay is something like full nodes sharing BIP 157 style filters instead of the transactions themselves, and only sending tx's that the peer doesn't match out of the filter set. I'm not sure how much this is actually more efficient or not...

I'm also not sure how this fits in to the idea of clients giving belated shout outs to a sprinkling of their nodes based on their reliability in order to shape the peer list to reduce bad nodes getting free advertising.

Anyhoo, the OP is just to note down what I figured out last night thinking about the problem of sybils trying to capture sessions and not deliver on them.