I have an older modem (DCM476) and it definitely doesn't have this or doesn't have it enabled. I have to use/tune queue management myself on the router side.
Yes, it's mandatory only as of DOCSIS 3.1, and yours seems to be 3.0. (Supposedly it has been "backported" to 3.0, but that obviously would not apply to existing devices certified before that amendment to the spec.)