mrleffan, Hey you're right! And as I take another look at it, in the last panel his cup on the table is slightly closer to the edge. I stand corrected. I can only assume that Wally came to the meeting with a cup of coffee in each hand. That is within his character.
seisho, I'm not so sure, if you notice PHB has leaned back slightly (so less of his chair is showing), and Wally is leaning forward slightly (more of his chair is showing), that doesn't look lik SA just copied it.
Chances are Mr. Adams just made a copy the first panel only changing the PHB's mouth and Wally's arm, and in the process overlooked getting rid of the extra mug. Otherwise everything else looks identical.