I still believe it's luck more than some fancy algorithm etc. at work.
It's too random for my liking and recent trips have had 3 people in my row with other also generic rows (i.e. not exit rows but say 3/4 of the way back on the starboard side) being filled with 1 or 2 people only (sometimes I get a GGL / GCH greeting in my full row whereas they don't).