Say we have a random number generator. It generates 2000 numbers that we put in two arrays, 1000 numbers each. Like this (here shorter arrays used to illustrate the point):

[4, 20, 5, 6]

[7, 21, 3, 3]

Then we sort each array and get:

[4, 5, 6, 20]

[3, 3, 7, 21]

Then we compare corresponding numbers in arrays and generate another with true/false (true if the number at position *i* is higher in the second array from the number in the first array):

[false, false, true, true]

For large arrays I would expect the number of falses to be more or less equal to the number of trues. (Almost exactly as in fair coin toss). However, when I use computer's random number generator (supposedly cryptographically secure) I almost always get large disproportion of one vs the other. Why is that?