>>151174559
The plastic Malcador was made by a different part of GW called Specialist Games that has its own Gamelines, Horus Heresy and The Old World, and at some point, it was decided that neither game lines could cross over with the mainline studio games of 40k and Age of Sigmar.
The Macharius is unlikely to get a plastic kit anytime soon due to this forced split between Specialist games and the Mainline GW studio, since that tank originated from a 40k book series called Imperial Armour, which was written by Forgeworld, which was later turned into Specialist games.
This studio split is also why the HH Mechanicum and 40k Mechanicus have completely different design aesthetics and play styles