Why do cameras update ROIPosition value to multiples of 4 or 8?

While troubleshooting the following warning during video collection with the Image Acquisition Toolbox,

vid.ROIPosition = [775 675 400 400] % The region of interest I wanted
preview(vid)
Warning: ROIPosition property modified to nearest values acceptable to camera. 
vid.ROIPosition
ans =
 772   672   400   400 % The region of interest the camera chose

I found this answer which states "Commonly, devices [like cameras] will require the size of offset values [in the ROI] to be multiples of four or eight." Any idea why? Could this be because of binning?