Here are some threads a search turned up for reflection:
What defines 'Sight Height'?
measuring scope height using canted bases
What does sight height represent in hollands software program?
Measuring Scope Height??
Sight height measurement
scope height measurement
I think you'll have a hard time coming up with a written reference/definition for this...your best bet if your after that would be to contact your ballistic software producer, and ask what their definition is/how it applies to your specific software.
My opinion-If pressed for an answer, mine would be the "sight height" would be defined as the point/axis where the rifle is rotated when changes in the elevation turret were made on the optic in order to point or aim the rifle at the same target.
Another thought-There might be more worthwhile things in your shooting system to dedicate time/thought too. It was calculated in one of the previous threads linked above that a 20 MOA base is less than .07 difference between the objective height and eyepiece height on a 12" scope....when I apply a .07 variation to sight height, I see no difference in dialed elevation adjustment out to 1500 yds. But like you....I can't stand to be ".07" off on anything
BTW-Those two opinions wasn't formed from any scientific knowledge/analysis, or special prowess on my part, but rather from conversations with some LR "sages" on this board and others in the precision shooting community. My 2 cents...but just barely worth 2 cents