The flashing red usually starts pretty soon after the green, you usually can't cross entirely on a green. It doesn't mean the person was slow or jumped the light.
Some other nitpicks: As a car, you have to wait until everyone is finished crossing. You can't just sneak through the middle, or cut just behind someone.
Unrelated to lights but tangential, you have to give way to all existing traffic when entering a road. That means if you take a turn, and someone is crossing the road ahead of you, you have to wait. They couldn't know you were about to barell around the corner, and they are under no obligation to hurry out of your way. No stress, you will be gone in seconds.