Fun bit about Radix is it really scales well if your dataset fits in memory. Last time I benched my lame Java implementation it was about 2-5x faster than the built in Arrays.sort() on native values(float, int) and 20x faster when you started putting it up against Comparable. Trended that way well up to 65k+ entries.
It gets even better if you can drop down to a proper native language that lets you prefetch.
Absolutely. But the impression I get from the article isn't that they benchmarked their solution vs R-trees or S2 and it proved quicker, rather it seems to me they didn't bother trying the other approaches at all because of their perceived complexity. I might have the wrong end of the stick because the article doesn't go into enough detail to truly know either way. If they really didn't benchmark any other algorithms then talking about the performance of the language seems somewhat moot.
I always have fun trotting out Radix Sort and watching fresh CS grads try to understand how a O(kN) walks over O(NlogN) by a factor of 10x+.