I also respectively disagree with your opinion.
How can a bus bar not be considered a conductor?
Since the NEC provides only 3 definitions in Article 100 for "conductor", none of which specifically says it has to be a wire, take a look at how Wikipedia defines an electrical conductor.
"Electrical conductor
In science and engineering, a conductor is a material which contains movable electric charges. In metallic conductors, such as copper or aluminium, the movable charged particles are electrons (See electrical conduction). Positive charges may also be mobile in the form of atoms in a lattice missing electrons (called "holes") or ions, such as in the electrolyte of a battery.
I don't see where a conductor has to be a "wire" by that definition.
Why would the NEC give us a calculation for Bus bar amperage if its not to be considered and used as a conductor?
Instead of running conduit and "wire" up a high rise to feed services, we install bus duct, which performs the same function as the conduit and "wire conductors".
So I would consider the bus bar in a MSB as the "circuit conductor" supplying the next level of overcurrent protective devices.
Just my opinion
COTInspector