"We detected that the model had converged by looking for 1024 training batches with perfect predictions, and that it could perfectly run 100 Life games for 100 steps." This would be superfluous (and even a pretty bizarre methodology) if the shape of the attention matrix was proof that the Network performed the actual game of life algorithm.
Just to be clear, I am not saying that the NN isn't converging to performing some computation that would also be seen in other algorithms. I am saying that the paper does not investigate whether the resulting NN actually performs the game of life algorithm. The convolution part is certainly evidence, but I think it would have been worthwhile to look at the actual resulting Net and figure out if the trained weights together actually formed an algorithm. This is also the only way to determine the truth of the initial claim, that this isn't just a statistical model, but rather an actual algorithm.