Unusual Banana bench results

Like all gamers, I like my good hardware, and I managed to obtain an 18 core processor (its overkill I know, I got it under very unusual circumstance). However, the results don't make sense to me. The performance is okay, but I don't understand why the Mbeams/s drops after the 17/18 core, then slowly starts climbing back up. I was under the impression that the engine was using a core per car. It isn't overheating, it isn't dropping frequency, it isn't even reaching tdp. Every run looks similar to this. I've run it no services in the taskbar, and its still the same. I don't know what's causing it.

 

it only uses 10 cores afiak

 

That... make everything make sense now. Thank you. Does the actual game do this as well?

Edit: Nevermind it uses the whole thing. My brain turned off for a second.