Honestly, while I wish they had included two head sculpts for Obi Wan like on the original Mythos statue, I don't feel too bad about it, what with Obi Wan getting a spinoff movie and all...
I mean, think about it. Sure, we're almost guaranteed to see a Hot Toys figure in a few years based on McGregor's likeness as a grizzled veteran in the Obi-Wan TV series. But we'll almost definitely never see a live incarnation of Guinness's Obi-Wan for Hot Toys to make a figure out of.
So, the way I see it, this is the Guinness Obi-Wan that we'll never see, but will live on in our imagination. Hence the mythos tag- after all, isn't mythos based on portrayals of characters in stages of their lives that won't be visually represented on screen?
Ironically, with McGregor playing the same era Obi-Wan soon, he kind of just got eliminated from being classified as a mythos figure...
As a sidenote, if you want a McGregor bust for this guy, just wait till he gets his own figure several years from now and plop the head on this body. Done.