From my vast experience of playing games with vanquish I see it likely that Marti is telling the truth. You have a tendency to steal kills to up your stats vanqy.
"My girlfriend told me to treat her like a princess so I bought her a Mercedes and drove her into a wall "
I thought you were just exercising your saintly nature by being kind and damaging the enemies for me every time to build my confidence and help me feel as though I'm doing well. Seems I was mistaken C4rma