Mainline is incredibly frugal in terms of resource use, but we want it disabled by default so mobile apps don't look like bittorrent clients and get flagged by the OS.
When we do a p2p address lookup, every mainline server node could possibly be responding. Any bep_0044 record gets stored on 20 random mainline server nodes.
So a bittorrent client that participates in the DHT as a server and is long running enough to be included into the DHT routing tables will respond, yes.
Bravo, because they always get it wrong.
DHTs used for decentralized DNS-like naming purposes have truly unique scaling requirements; you have to use a connectionless protocol (like bittorrent does) but everybody seems to be fixated on connection-oriented protocols like TCP, HTTP, and QUIC. The latter just don't work for this extreme use case.
No other use case on the entire internet requires such an extremely large out-degree for end-user nodes in the node connection graph. Allocating connection-state, even a very small amount, opens up the least-powerful nodes to easy DoS attacks. And from there it's easy for a motivated attacker to push the network away from decentralization and force it in to a highly-centralized state.
But at this point it is just a toy project to push the limits of what is possible with iroh and 0-rtt. It is not used in prod and won't be any time soon :-)