I also agree with you. First of all, 400 may fit for the current system but we haven't found any good number for the modified n. And if the number is high, there are only few posts that become close-to-linearity while other posts are still suffering far below the n line. This will make more people and bots to choose few high-ranked posts and consequently current problem cannot resolved much.

If we lower the number in denominator (e.g. 400 to 50), posts with over 5000 MV votes already have approximately 99% of linearity so there's not much difference in piling effects between posts with 5000 MV and with 50000 MV.