I see quite a few mono p.d's that are 5 to 6 mm difference, like 28 / 34 sent to our lab. Back when I used to take mono p.d's the old fashioned way with p.d. rule.
1st measuring binocular, then from center of bridge to right pupil and then from center of bridge to left pupil, it wasn't perfect, but with double checking by marking the demo lenses it usually worked out well.
I just don't remember p.d's being up to 6mm difference as often as I see it nowadays.
Thoughts?