irregularity in a tile jig is very common it can be small are large depending on manufacturer and QC, it throws of the true square of the material it can be counteracted by setting the tile in the pattern i posted that the good Lord himself sent me in a vision for the tile community to benefit from .I completely missing the point as to why this works in any way shape or form. Also are you talking about irregular shaped tiles rather than square tiles which may have a difference in size between tile to tile
Try it out for yourself