What I'm saying is that if the video card you were using had 16 lanes available and got X performance. Then you took away half the lanes available to graphics c

What I'm saying is that if the video card you were using had 16 lanes available and got X performance. Then you took away half the lanes available to graphics card, so now you have 8 lanes available, but performance has only decreased by 20%. Meaning that the game or application was only using a fraction of those extra lanes. So basically it wasn't fully exploiting the hardware available.