Oh, I guess I can think of one way a couple minutes of light might matter.

Let's say the maximum light time your weed will take and still flower is 13 1/2 hours. Your timer is set up for 13 hours and 28 minutes of light. If you open the door EVERY day for 2 minutes during dark, I could see this might be a problem. Otherwise, most people set the timer for 12 hours of light, when the plant can actually handle a lot more and still bud. It varies per variety. I am growing AK-47 and have my lights on for 12 1/2 hours. I think I remember reading that they will bud nicely with 13 hours of light, so why the hell does it matter if I occasionally give them 12 hours and 32 minutes of light?

And again, why the hell does it matter if the plants suck moisture up into the plant matter at night, and it is there waiting when the light comes on, or if the light comes on, then the plant has to wait around a little for some water? Actually that might be a good reason against watering in the morning, unless you are always able to do it the instant the lights come on. I assume the whole idea of this debat is that it's best to water the instant the lights come on. Who does that?