Could improper deplaning of a flight with full fuel tanks cause the plane to tip? Reading this article regarding an Alaska Airlines 737 Flight that had to turn around back to the gate. There was a following statement:


  At the gate, passengers were unloaded five rows at a time, to minimize the risk that the plane would tip under extra weight of fuel. 


My general understanding is that the fuel tanks are usually placed near the COG (wings, cargo tanks). Assuming the tanks are still full, why would unloading of passengers all at one time possibly cause the plane to tip? Or is this bad reporting?
The 737-900ER has (two) auxiliary fuel tanks in the aft cargo compartment, behind the wing (and center of gravity) with ~3400l capacity for increasing range (from 2800nm to 3,200nm). 

In usual conditions, unloading of passengers wouldn't be a problem as the fuel would've been used up; However, as this was an overweight landing with full fuel tanks (the auxiliary fuel tanks weigh ~ 3t), the crew are just being cautious to prevent any incidents.