IMO, Vdb and Negronne are the same or vary closely related. If they are in fact different, it is my opinion that both have been sold under both names and interchanged repeatedly, and, short of DNA testing, there would be no way to tell them apart if they are in fact two different varieties. It is interesting to note that the leaves of VdB and Negronne are very close or the same, even though both display a wide variety of leaves from single lobed to 7 lobed. The predominant pattern is a very distinct 3 lobe shape that I have not seen exhibited by any other variety.
Having said that, it is also my opinion that there could be different "strains" that could show different characteristics which could lead someone to think they are different varieties, or because figs are so responsive to their environment (soil, weather, fertilizer, breed of neighbor's dog, etc.) the differences may only be cultural. I have done this over the years with 2 dozen Celeste "strains" and other tests. I can spot a Celeste from my orchard, even though they all look different. On any given day, almost any tree can have any of the various "looks" but some "looks" seem to predominate on certain trees. I can show you all the characteristics that help identify a Celeste fig, but after sorting though hundreds and hundreds of pictures, I cannot show you a picture that actually embodies all of the characteristics, or in the proper proportion, of what might be called the perfect or ideal Celeste "look". And then when you move them to Texas, or North Carolina, or Michigan, They often have few if any of the characteristics which are so typical at my location - to the point that I likely would not recognize them.
All that to say, they are one and the same and no one can prove otherwise.