The QUBE DCS system which does the weight + balance does not care about lateral stability.
It does however check-in after using rows 3-7 first it then starts at row 23EF then 22AB then 21EF going forward. It will try to put the same weight on each side of the aircraft.
However at the end the Load Controller is presented with a Weight for 3 pax zones in the 737 based on front to back situation. There is no data for side to side seating config.
The 737-300/400 needs weight in the tail to trim it nicely - it is hard to go outside the aft CoG but is easy to go out the forward CoG.
If there are not much baggage to stow in the aft hold the only thing left for the load controller is to walk pax to rear of the aircraft.
On a light load (<30pax) I don't allow any seating in rows 1-7.
Also if the flight is running late and the loaders have stuffed up the bags by putting them in the wrong hold (happens all the time - they don't listen or understand plain english!) then the quickest solution is to move pax and get the flight out.