I think it's a combination of the very high velocity and the height of the ring/base/scope combo.One and a half high at 100 may work for a 200 yard zero and a standard cartridge with more moderate velocity(say a 270-130 or 30/06 165),but IME when velocities get real high with a slippery bullet in the 3500 FPS range,mid range trajectory rises REAL fast,and every combo requires careful confirmation, as you have done.
I don't know how high above the bore your scope is mounted,but suspect you are using "medium" rings;and the base is likely machined to allow LR reach;I am not familiar with the set up.But all these factors, along with the very high velocity conspire to cause a very high mid-range trajectory.
Some VERY slippery bullets can cause this as well,and using the 150 Scirrocco from a 7 mag at 3150(low rings) I found I could not use a 3" high zero at 100 yards,as mid range was very high,and I was only a bit low at 400 yards.I had to rezero to be no more than 2" high at 100,and then my trajectory got closer to being "normal".Ditto with things like a 7mm 120 TTSX at 3550;and a 130 TSX at 3600 from a 300 Win mag.
You might want to lower your 100 yard zero to no more than 1" high,and shoot to verify.Hope this helps.
