I also thought it was a mistake because shortly after it in the photos Riley sent me was this:
In the second photo, you can see that her right arm is bent and she is leaning her weight on her elbow.
I *think* though I am not sure, because this is a part Jim wrote and I haven't talked to him about it yet, that putting your weight on your arm at all is something you do in the drill to prevent your opponent from being face-planted into the mat as you do a wake gatame.
In competition, though, I would think you would not put your arm there to slow yourself down and it would be,
"Face, say hello to mat."