Ahh I see, I thought it was a gravity simulation, not attraction based on mass.
Now that I look at your links in the original post I see that it is happening in your examples. The cubes with mass 10 in your example should move exactly the same as the cubes with mass 1. The pull of gravity is identical on all objects regardless of their mass.
I've found that if I launch a spacecraft away from a planet then turn off the thrust your gravity model will slow it down much quicker if it has a high mass... whereas any object should slow down at the same set rate.
This might be a flaw with unity possibly, not sure how realistic the default gravity is but I had thought force type "acceleration" ignored mass.