RT-AC66U_B1 not using 2nd CPU core

I have it setup with Download QoS Only at 102Mbps. While running The latest version of Merlin. My CPU 1 maxes out at 85%+ While downloading. While CPU 2 is sitting at 5% or less not being used. Is this normal? While downloading it seems to really slow down YouTube videos from loading etc. BUT EdgeRouter X starts a YouTube video just fine while at the same time maxing out my connection.

And another thing, QoS is not working which is what I was afraid of. I'm using adaptive which works...

RT-AC66U_B1 not using 2nd CPU core