Having considered it and slept on it, I believe JM stipulated because he did not want the goofy line drawing admitted. The 'tracing' would be the source of much confusion. I believe that if JSKS admitted it under Rule 702, eventually the 16 remaining jurors would have had to be transported to Neumeister's lab in order to 'see' the blob his way on his equipment, leading to even more histrionics and over-emphasis on Guesstimony as fact. Not to mention further delays and added confusion.
Moreover, if established in at least one juror's mind, it would place the defendant standing fully erect near the time she initial attacked Travis in the shower. While she certainly wouldn't have taken more than a second to bend or crouch, juror confusion is not good for the State's case.
It appears that JM's calculus was that the picture, being framed so obviously intentionally, was taken by the photographer with both hands while looking through the viewfinder, and crouching as the defendant herself testified, and not standing, with the camera held below the chest and lower on the torso, in the neighborhood of the navel, as Neumeister claims.
Is having jurors understand that JA was crouching, not standing, when she took that photo damaging to the State's case? Or does it actually comport more with the State's version of events? Obviously, JM thinks the latter is true.