Hello Manie,

this is a general requirement for QoS on multilayer switches.

Each frame or packet is associated with an internal QoS tag that by implementation choice is a DSCP field

As a result of this CEF is needed

To be noted in multilayer switches disabling CEF is  impossible they need it.

On SW based  routers almost all modern QoS tools require CEF to be enabled and even less recent tools like CAR, so it is not a surprise that CEF has to be enabled to support autoQoS

Hope to help

Giuseppe