It'll eb as simple as the angle of the throttle pedal is greater than you think. You're reacting to a light going green and hitting the throttle. You'll just be hitting it hard enough for the software to think you want kick-down and it'll drop a cog.
I'm sure it's frustrating but I also think it's perfectly normal behaviour. Even a transmission as good as the 8AT can't read you mind and is only acting as the programmers designed it