I agree with the people before me - the assumption that killing Lupi and Co. somehow alters drop rates is baseless superstition, and with drop rates as ridiculously low as they are, it's virtually impossible to prove anything one way or the other. It would take thousands of runs to make any sort of statement of statistical significance about it.
What I can tell you is that I've done more SF runs than I care to remember - solo runs, team runs, heck, I even solo'd a team run - but I've never seen a unique drop.
I almost never kill Lupi and friends in my runs. Not because of the superstition, mind you, but rather because they don't attack me, and I therefore couldn't be bothered to waste a chakra-filled bullet on them.