If there is money heavy on the Pats, books may have decided to take a side on this game. Meaning they like the Chiefs, and are willing to expose themselves to a loss, though thinking the Chiefs will come thru. There main objective is obviously to balance action and collect juice, but on a few games they will take a stance. Not sure if that's the case this game tho. Also, many books would be reluctant to move off a key number such as 3.
Just my 2c worth, Jono.