It is merely another form of communication - body language that says "I'm ready when you are...".
Yes, that's one way of looking at it
But I interpret it as :
"you should be calling for gear and flap THIS MOMENT NOW, let me remind you, as this is when I would be calling for it. I got no regard for SOP's or other techniques within the SOP's. I know better than anyone else or the book. This action must be done now when I say"
or
"you are totally incompetent and I have no trust in your flying ability. I always have to drop subtle hints to you"
or
"you might be the Pilot Flying / Handling Pilot, however, "I, the captain" still have ultimate control and will control how you fly. I alone will make the decision when to operate the gear and flaps, and not you on your call. I will talk you through everything you do"