This was super interesting, thank you for sharing!
At one point in the dim past I wrote an xmodem implementation for the 8-bit atari so I could download at 300 paud from compuserve, and I remember seeing "antileech" mentioned on various BBSs later - but never realized they were referring to an actual thing, I thought it was a warning to share.
In hindsight the exploit seems obvious, but it would never have occurred to me to not follow the protocol at the time. I was... innocent.