Well, what I explained above was mostly about the dynamic behavior the AGC expects, mass shifts are not currently simulated, but might be in the future. We might make NASSP more realistic with changing center of mass, if it is possible. However, as you can see in the video, the TVC DAP is working and it is using the historically correct parameters, so no hurry for these kind of changes.
One point with regards to the SPS gimballing is however kind of dynamically changing already. Basically, the neutral setting of the SPS is angled 2° in pitch and 1° in yaw. But because the CSM is a perfect point mass with the center of gravity right in the center of the spacecraft, the SPS engine in NASSP has a slightly offset position so that it points through the center of gravity in this neutral setting. Now, with the docked Lunar Module, the SPS engine and the CSM and the LM are not on a straight line because of that. So in the docked configuration, the SPS doesn't gimbal around 0 but depending on the masses of the CSM and the LM.