This is interesting. I assume your measurements are like the two longer lines in the attached photo (sorry about quality, cell phone camera). If that's correct, then on my instrument, the line to the G/D touchpiece is approx 62cm and the line to low Eb touchpiece is 66cm (65cm to the very tip of the low Eb touchpiece).
It's actually interesting that exactly those keys, from G/D down, are not closed directly by the fingers (on some instruments the A/E key isn't either). On my instrument it is a little crowded around the A/E, banana B/F# trill and G/D keys, not in any way that causes a problem to play them, but the design is careful to comfort and intonation of Bb/F (which has its tone hole close by a finger). Maybe some instruments had these keys (G/D down) a bit farther away from the others, for an easier design (less trouble trying to fit everything in a crowded area). Just a guess, maybe it's not like that at all.
Can you also measure the third line in this photo? This is perpendicular to the body, from the end of the mouthpiece socket farthest part to the part of the body farther from it, forming a right angle with the body. This is to see the "length" of the neck, regardless of height. Eventhough the Buffet is not as squeezed as the curvier Selmer neck, I'm wondering if they squeezed it some. I get 19cm on mine.
BTW I also checked the angle of the neck (mouthpiece end) relative to the body. It's not so accurate, I just put an "angle measurer" (don't know the name in English for this) next to it and it looks like it's about 50 degrees between neck end and floor.
And while we are at it - place your right hand on your belly button, so that the hand knuckles form a vertical line. How much further down can you move your hand so that the knuckles are still vertical?
I get ~57 cm from the tip of my chin (straight head position) to the index finger knuckle. Stretching more is nearly impossible.
I'm not sure I understand. Do you mean hold the hand so the fingers are perpendicular to the stomach, with the pointer above (looking down) the others? Then move until I can't have the pointer in front of the other fingers i.e. have to turn my "hand"? If this is what you mean, it's already pretty uncomfortable when it's at my belly button and I can't move it much lower than that. If that is what you meant, I can get to about 55cm but it's pretty painful
But I'm pretty sure I ddin't understand your description right.