Your photo is irrelevant if the ship has already attained cruising speed i.e. turbines have already been ramped up, boilers have already been fired, fuel mix is already optimal, hence no black smoke.
Read mine and others' comments carefully instead of rebutting willy-nilly. The carrier doesn't wait "until mid-takeoff" to fire up boilers. Boilers were already in process of firing up, turbines already in process of revving up, and as they do so the boat picks up speed. Then what happens? Black smoke spews out.
As she picks up speed and once she attains the desired wind speed over deck e.g. 30-40kn, aircraft gets to launch.
So here's an easy explanation, not hard at all - Likely scenario where the boat was already at 20kn but wind speed dropped from 10kn to 5kn, so she needed the extra juice to conduct flight ops. What happens then? Additional boilers are fired up. Here's your black smoke.
And as it happens we pass 30kn and birdie gets to fly. So the air boss says "Go!" without delay. Mind you the boat is still speeding up, as the boilers were still firing up and black smoke getting photographed for this back-and-forth debate. Why? They got the speed, speed is good to go, bird goes. What else they gonna wait for?