Those who had simpler heuristics did better. Trying to combine 4-5 heuristics is hard, as you have to weight them against each other. The "gradients" mentioned here did alone produce good results for most students. Of the ~50 people, most managed to demonstrate to me that they could get a 2048 tile within a time limit. Some even 8k and 16k tiles.
I think most of them got the "Tetris-effect" by watching their bot play a few rounds, tweak, run it again etc. for a few days. Probably watched blocks sliding around when making food etc. :p
Also a very interesting read.