John Any circuit that starts at one Over Current Protective Device (OCPD) and supplies other OCPDs is by definition a feeder vis.
ARTICLE 100 Definitions... Feeder. All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device...
Since the "final branch-circuit overcurrent device" are the circuit breakers that protect the branch circuits which are located in the panel in the garage the circuit that supplies that panel is a feeder. The exception in the NEC is meant to exempt small sheds or out buildings that are literally supplied by a branch circuit. To be a branch circuit the last OCPD has to be at it's source.
Branch Circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
That exception that exempts buildings supplied by a branch circuit from the requirement for a grounding electrode system has a companion exception that exempts such buildings on residential property from having a building disconnecting means that is listed as "Suitable for Use as Service Equipment" The exception says
225.36 Suitable for Service Equipment. The disconnecting means specified in 225.31 shall be suitable for use as service equipment. Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.When taken together the requirements for buildings that are supplied from a service that is located in another building come down to all buildings must have a disconnecting means. All buildings supplied by a feeder or service must have a grounding electrode system. The disconnecting means must be bonded to the grounding electrode system by a properly sized Grounding Electrode Conductor.
I am not being so insistent in order to be argumentative but rather because I don't want neophyte DIYs to follow unclear or misguided advice and come to harm.
-- Tom H