Agent has closed-out the flight + cockpit is ready + cabin is secure = Clear to Close! Trigger the Out time the second L1 is armed. Nobody enforces the early departure guidance, because CPZ makes more $ in On-Time than they do in paying Overblocks.
Plus what’s the point in sitting there when the sponsor airline has already closed out the flight. Customers care about A0 and flying fast. Sometimes you have to drop early in order to make A0. D0 is nice in a perfect cubicle...I mean world.