The solution here is faster than the absolute naive solution of finding all distances, but it is both slower and less readable than integer math grid conversion..

I could see why you would make the choice of the naive, slow solution. I could see why you would choose the fast, integer math grid conversion one. But I don't see why you would choose something slower than the optimum solution that is also much, much less readable.

That is, the naive solution and the integer math solution are Pareto-optimal choices... and this abomination ain't.