I was looking through my stats in the game, and came across this interesting line in the details/vehicles section:
(edited in paint to shrink it down):

https://i85.photobucket.com/albums/k74/FrenziedAU/dodgystats.jpg

Now, as far as I know the K/D ratio is simply kills divided by deaths, both using the values shown, therefore unless the 'deaths' used for the K/D ratio is something not shown...