To expand on what Scotty said: I won’t pretend to know all the details, but the general rule for making minis is that Catalyst must have published art of some version of the unit in question, so that the mini can be based on said art. The new locust, gún, and lu wei bing all have art that appeared in official Catalyst products. None of them were based on MWO art.
However, the lead concept artist for MWO has done contract art for Catalyst in the past, and some of his designs look similar for both companies. He did the Lu Wei bing, which shares a lot of elements with what he did for the MWO Victor. The Gún was his art, but the new locust about to come out in the box set is based on work from a different artist. You can see it if you look up the Locust 1V on the MUL.
So, no MWO designs (and no HBS either!), despite the fact that a few units do look very similar.