I'm not familiar with that intersection... but here by me, we have one where they marked off the box like this, with signs that people on the main road must not come to a stop in the box... but this is specifically to allow people from the side road to be able to pull out onto the main road, into the box.

Essentially forcing people to let people in from the side road.

It's a clusterfuck of an intersection for sure, designed at a time long before it got so busy... what it really needs is a second traffic light, but it's very close to the main light so I guess that's why they don't.