| I think but could be wrong that what's happening is this:
Mike is moving from the Development (tweaking, testing, checking, revising, poking, prodding) team to the design (crazy ideas, odd thoughts, new stuff, drive developers crazy) team. He's also going to be leading that team.
Rob is giving up leading the team, and going (back?) to being a member of it - so he gets to do more design than Mike (and than he was doing before) as Mike gets the leadership/direction/strategic/managementish stuff to do.
That's just based on the words used in the post though - there could be other stuff going on, I'm just trying to interpret what was said. | 
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