It has been very thoroughly studied, chemically, and with radar and infrared. They have even found LDV's fingerprint in the paint. It is now undisputed. Moreover, after spending many hours staring at it over many years I can assure you that it is a remarkable masterpiece. There is a certain compositional arrangement that gives it the classic mark of a genius, but I have never seen it commented upon. Moreoever, if you look carefully at the control of color and tone on the face, the incredibly subtle shadow, and the shear fabric at her throat, there can be no question of the mastery with which this is painted.
It is like one of those Shakesperian authorship problems. If it is not by Da Vinci, then there must have been a second genius of his stature.
You may know more about this than I do, but even the folks at NGA as recently as last summer, which was the last time I was standing by the painting, acknowledge that some dispute whether it is da Vinci's. I certainly lack any expertise to tell. The arguments you make (mostly) are the ones the NGA folks make as they claim it is a da Vinci. I would note that Wiki (not always the greatest authority, but it's handy) says that Ginevra de' Benci is "attributed" to da Vinci while the Mona Lisa was "painted" by da Vinci.
ML/NJ