Whatever way you measure the pitches, as long as you use the same technique on the next ball, it will match. So by measuring a 45* thumb's pitches after the fact(whatever they may be), obviously the t grip pitches will be diffent. Now use those t grip pitches to drill the ball the standard t grip way and you arrive at the same results. If my front to back and side to side pitches match from one ball to the next, obviosuly, if I measure pitches at a 45* angle, they will match also.
And using Jayhawk's(PAI's) digital pitch gauge, I believe it will accurately measure pitches on oval holes.