As far as I am aware there is no documented requirement to hold the wheel forward after touch-down in the B737. The ground spoilers have already done the job of putting the weight on the wheels.
However, I have noticed that in the 737 simulator, pilots that have come from prop aircraft to fly the 737 for the first time, almost universally apply forward stick after touch-down and during reverse thrust. I believe that they have brought this habit from previous aircraft which are not spoiler equipped and in which forward stick puts more weight on wheels for better braking.
Similarly I often hear ex prop pilots replying to the B737 80 knots call by the PNF on take-off, as "I have control" instead of just the basic acknowledgement word of "Check". This also probably stems from the transfer from nosewheel steering to rudder control around 80 knots in some turbo-prop types.