If the yellow light were longer, he might have entered into the intersection still on a yellow light instead of red. The length of yellow light is to give time to react and safely stop *before* entering the intersection. The time it takes to get through an intersection should be addressed by the "all-red" clearance time. Traffic lights govern entering the intersection, not exiting it.
Short yellow lights are key to these cameras generating revenue, and directly counter to safety. A huge fraction (often >80%) of violations come in the first few tenths of a second--well before the other direction sees a green light.