The feedwe is still only supplying all the power for the single dwelling unit. No common area. No other unit. If you are splitting hairs over a grage parking space then we would have to say the same to a outside deck, or a shed, or .........anything.
The code section you cited speaks of the entire load associated with.....
The way it was explained to me was if the feeder split to feed another item not just to the singular related load ie the apt panel, it is a feeder tap, it also is provided a seperate overcurent protection.
As opposed the argument above for the outside shed or deck, which is a description is of a branch circuit not a feeder. If those items had a seperate panel or overcurrent protection remotely or seperate from that provided in the source panel it is then no longer a branch circuit but is a feeder circuit.
This item even though a rather complex one is a tap. The feeder once it is tapped it is no longer providing providing the entire load. The internal tap portion doesn't need to meet the feeder requirements but also the extended portion from that breaker to the EV charger is a branch circuit of the device, the continuation of the apt feed from that device is still a feeder and is required to meet the limitations of a feeder and is not carrying 100% of the load as part of it is distributed to the EV charger and the 83% allowance no longer applicable.
I could acquiesce to the idea that the feeder from the first overcurrent to the tap is providing 100% of load of a dwelling unit, but from that tap to the apt is no longer carrying 100% of the load but only a proportional portion relative to the total loads applied to the apt and EV charger combined.