check the setting, ipv4 fast path is active, but ipv4 fast path packets is alway 0,
so confirm CHR support fast path?
routeros: 6.40.8 chr, no queue, no firewall list, connections tracking no

CHR does not support FastPath, yet…
but the official presentation said the chr version support fastpath.
https://mum.mikrotik.com/presentations/EU16/presentation_3098_1456817868.pdf

Also have this question.
Any official comments?

The presentation says the VMXNET3 NIC supports fastpath. Are you using that?
What packets exactly are you thinking you are fast pathing"ing"? From? To?
CHR always uses VMXNET3