It’s just an automated account showing who is DMing who. The note type for DMs includes the public key of each party and an encrypted payload. There’s a calculation to estimate the size of the message based on the size of the encrypted message.

See here: https://github.com/nostr-protocol/nips/blob/master/04.md

Their challenge is to the way NIP-04 works and the disclosure of the parties involved in the DM.