Nobody is going to the trouble of getting their target to set up cryptography tools so they can pass private messages back and forth between public channels.
They're going to move to another platform where they can find targets who have DM functionality available. BlueSky's job is done.
Having to delete the obvious spam "hello" DMs in Telegram is so much fun... Fortunately I'm not that active and only in a couple channels. I still see a couple a day (block/report, etc).
Anyone can easily circumvent this by using asymmetric cryptography to encrypt their messages.