That's such a shit take since it ignores so many key aspects of the game.
A duelist's role is not to get kills but to get space. If you get openings kills and multifrags as a result of that space, great, but if your duelist is consistently getting your team on sites by taking space but get no entry kills, that will help your team massively. They might bottomfrag but actually help your team win in a huge way.
Also, that would promote people to play in non-optimal ways to "inflate their stats".
If kills mattered a lot as a duelist you could lurk all game and play 1v4 situations all the time to get exit frags and boost your RR gains. If util usage mattered a lot more as an initiator or something, you'd be using your util to affect the maximum amount of enemies no matter if your team can capitilize on that utility or not.
Piss take and stop crying about losing.