A couple of months ago I downloaded a 1970/80s movie that was so obscure only private trackers had it. I am virtually the only seeder, my radio is currently 1.8 which is the highest I have. (Might not be high for others, but I just download 10yo tv shows that have soo many seeders they dont do much)

The readings will have an extremely low signal to noise ratio, at best you coils differentiate a truck from car by length of the pulse, but with speed already being ±30% variability any small difference in cars inherent properties (size in length or amount of metal) would quickly be reduced to nothing. Then for every make and model you have thousands of cars already, I don’t see how you could possibly differentiate between those even in theory.