Thats a very weak excuse. Really the true question here from a grappling perspective is does my grappling work when people are trying to punch me on the ground.
It obviously doesnt prove anything if he just gets KTFO standing trying to strike or initiate a clinch like what basically happened to Roger, other than affirming what we already know that BJJ or any one style isnt enough on its own.
What he really can do to answer this question from a purely combative grappling perspective is he needs to fight a fellow grappler in MMA who will grapple with him.
Be that Sambo, BJJ, Judo, Catch, a fighter who will tie up with him and then when they hit the mat or even just in clinch, will his grappling translate?
Think of Fedor nulifying Nogs guard from on top.
Unless he answers this question, he ever will remain a pampered and protected Amercian golden goose selling videos, and shouldn't be mentioned in the same breath as Combative grapplers who tested themselves in the arena of real fighting IMO.