100 yd zero usually results in about 1.5 to 2 inches low at 25 yds,depending on scope height.
to move up 2 inches at 25 yds requires roughly an 8 inch moa bump up. so yes a 25 yd zero can be around 8 inches high at 100 yds if he shot 1 inch high at 25 yds he would be 12 inches high at 100yds the higher the scope the worse these numbers will be