Did Cecil realize?

So, after the device in Mark’s head is turned off and he grabs Cecil by the throat (the first time), and he threatens Cecil, there’s a split second shot of Cecil’s face like he realized something… was that Cecil realizing that Mark was “bluffing” about killing him? I feel like it would be a good parallel with the scene of him meeting Nolan the first time and saying that he knew that Nolan was lying from his eyes. I generally know what happens in the comics but I have not read them myself, so I don’t know if this is explained or even in the comics or just for the show.