Very interesting that this is another post-TROS story, even if non-canon. The Lego Star Wars holiday special must have been successful and I wonder if this means anything for more future post sequel media.
Worth noting that a couple of the shorts from Visions will be set after TROS as well.
To be actually on-topic about the Halloween special itself, it sounds very like the ‘Vader’s Castle’ comics Cavan Scott wrote for IDW for Halloweens in 2018 and 19. I wonder if they actively used a similar premise without consulting Cavan, because he says he hasn’t been involved at all. I hope not, but Disney do have a bad habit of not consulting authors - Chuck Wendig had no idea his character Cobb Vanth was going to appear in The Mandalorian, for example.