I'm just trying to get across that there is very little hard science available on the subject and it's easy for what 'seems like a good idea' to become the perceived knowledge without any hard evidence.
There's also a lot of other factors like string break angle and the angle of the nut slot that can cause a buzzy nut, and these are probably the more likely cause of it than the shape of the bottom of the slot, but everything interacts, so nothing can really be taken in isolation.
I need to have a look at all my Hosco files, both the originals and the new black-bladed set, to see if their shapes vary at all, or they are all like the 0.050" file. I chose that one as it is the new addition to plug a gap and was unused, so there was no chance of wear modifying the shape of the file.