The recent O(n log n) algorithm is only useful for numbers of size larger than 2^(2^(9^12)). Which is to say, this will never be of practical use in our universe. (Of course, conceivably someone else could invent a different algorithm of the same asymptotic complexity with a more reasonable constant factor.)

But it’s still nice to have a proof that this lower bound is attainable in theory. Makes it easier to write down the theoretical lower bound for a wide variety of other algorithms.