After verification, I was indeed mistaken: with a scanner like the Nikon VED (which I also have), it is necessary to place the emulsion on the low side, ie in the direction of the scanning device. On a flatbed scanner (type Epson V500 / 700), it is the opposite.
Currently, I have abandoned (temporarily?) The VED scanner due to a change of PC: installation problems with the latest versions of Windows 10.
Now I “scan” with a macro lens: the advantage is that it is much faster and just as qualitative with the current sensor sizes. And above all it allows to have raw files to use directly in PhotoLab. The downside is that you cannot take advantage of the ICE to remove dust automatically.
I am not convinced that the emulsion / film orientation has a real importance for the sharpness of the image, at least with films not too old. I do not see a difference according to the direction with my macro lens device.
I think that the obligation to place the emulsion at the bottom with a VED is due to the internal Focus system which requires the emulsion side, and also the hardware ICE which can only work on this side. The V500 / 700 scanners only have a software ICE, and therefore do not have this obligation.