p2p leaks the 'metadata' of the network connections. It makes it trivial for someone to know that these two nodes are talking to each other. A goal of this, and other similar protocols, attempt to prevent that sort of metadata analysis.
If the peer selection protocol is something like a dht, or a random-k network like bitcoin, it doesn't leak anything.
but in practice nothing works better than all-to-all messages via epidemic routing. https://www.miasma.space/anon-dhts/