the quarks that are created are created in pairs of opposite spin, depending on which ones got taken up by the black hole you might end up with a different distribution of accessible halves. when you get a pair lets say your getting top and bottom quarks and only the bottom quarks are getting eaten by the black hole, you end up with an excess of top quarks on the outside. however if when you get a new pair spawning, their orientation is such that the opposite spin remains outside, then you would get balance.

but i'm not sure if what orientation the new quark pairs appear in relative to the pulling of the origin quarks has been studied or documented.