Yeah, but I think it was cause he was shocked/shattered as opposed to trying to pull something. I think he would have walked had, for some unknowable reason, Bucknor not given him - but it just would have taken him another second to snap out of his paralysis.
But of course, that's just speculation on my part. Unless Clarke comes out and explains why he paused, we'll never know for sure what, if anything, he was thinking. But I repeat, I find it inconceivable he was trying to bluff his way out of that - noone could think an umpire could make such a bad mistake. Or he had some kind of brain explosion and was trying to make some kind of smart-ass point which was obviously lost on all of us who weren't temporarily insane.