People have agendas for any random reasons... hell we have inner Morningbigblue agendas (TBURGESS,FLOYD, etc....)
For myself I come down Portage and turn left on Main street.... their is no possible way that 10 seconds would be tacked on only. I'm assuming he's cherry picking people coming down Main and turning right on Portage at the green arrow light and using best case scenarios (light traffic, a system that uses the button to activate the walking sign, minimal pedestrians attempting to cross etc...).
I'd assume what really would be set up is a 30 second timer to cross... people naturally trying to cross at the last second which would tack on a few more seconds.
I'd listen to Bellamy but it doesn't past the common sense test so at this point it's just b-s to me.