That's not correct. Torrent swarms and the DHT are separate. Each torrent basically forms its own small network of TCP connections to exchange data specific to that one torrent. While the DHT is a network shared by all clients that speak the protocol and it's carried over short-lived UDP query-response exchanges.
You have to be participating in a torrent swarm in order to bootstrap yourself into DHT at all. Bittorrent's DHT is not a network independent of torrent swarms. You need the address of a peer who is already part of the network in order to join it, and you have to get a list those addresses from somewhere.
Which of these methods is not obtaining the address of a node in a swarm, or hitting a tracker for a list of nodes in a swarm?
> People have used the DHT for non-torrent-related purposes.
This is simply non-responsive. People have used a DHT overlaid on the collection of torrent swarms for non-torrent related purposes.
> And nothing dictates that that has to be obtained via the bittorrent peer protocol.
This is a silly distinction. You also don't need to join a swarm to get on the DHT if I join a swarm to get on the DHT, write down the addresses I get on a piece of paper, then email you those addresses, which you plug into your handwritten specialized client that only knows how to join the DHT.