At those distances I could see that maybe it could affect you. It may be possible that the cross hair being unlevel may cause you to unintentionally square the rifle to the cross hairs instead of holding the rifle itself level.

Something tells me that your cross hairs are pretty level. You're just wondering if you should measure them to be sure?

You may want to get the opinion of one of the long range shooters on the forum like RR or others around here.

Tom