It looks like the person that made this program started playing around with the idea May 9 (https://twitter.com/probabletrain/status/1259172635776294912) a day after Dyson started tweeting about his program (https://twitter.com/DysonLogos/status/1258797586464542723).
I think Dyson's program is just a Photoshop extension and Dungeon Scrawl looks way more powerful, but it's worth pointing out the very similar timelines and styles.
https://twitter.com/watawatabou/status/1197194111171940352
(in aother tweet, @watawatabou attributes the style to Dyson, though the idea of doing it programatically).
Here are some tweets by the maker:
https://twitter.com/probabletrain/status/1259172635776294912... https://twitter.com/probabletrain/status/1258821040937013248...
https://archive.org/details/Dungeon_Magazine_002/page/n25/mo...
https://archive.org/details/Dungeon_Magazine_002/page/n45/mo...
https://archive.org/details/Dungeon_Magazine_002/page/n51/mo...
https://archive.org/details/Dungeon_Magazine_003/page/n31/mo...
https://archive.org/details/Dungeon_Magazine_003/page/n41/mo...