LC, you might be right, but you are overlooking a possibility.
What if Mr. McClain looked at the situation and asked to get reps at DT? He played there in HS. He has watched others play it at WSU for several years. Maybe he asked to try it himself?
It would not be the first time that has happened. He lacks an explosive burst, but he may be able to play NT. If he can learn to stay low and use his hands, he may even be an effective DT.
I don't know him at all. But I wouldn't discount the possibility that this position try out at D line might at least in part be his idea.