Yeah, that I2P example felt a bit off-base. Nodes self-announce their (network-respective) address for each network they support to each peer after establishing a connection, i.e., on clearnet, a node will announce its clearnet address to peers. Such peers may then forward the address when they get asked for a batch of addresses by another node. I don’t remember whether nodes only gossip addresses of the respective network on each network, or whether they generally gossip addresses from all addresses (probably the latter?), but a node that doesn’t use I2P wouldn’t announce an I2P address, so we’d never try to connect to it with I2P.