A quick hijack.
At the first means of disconnect, a main panel for example, the neutral/EGC bus bars are connected with a factory installed strap usually. Installation of the bonding screw does not connect EGCs and neutrals as they are already connected via the strap but the screw insures that in the future if a separate EGC bar is added then it is bonded to the supply neutral and also the screw bonds the enclosure to neutral to ensure a fault will clear if ever an ungrounded conductor faulted to the enclosure.
Correct?
Actually more on topic then past few posts have been.
Not quite able to fully agree with what you said, you are mostly on track but depending on exactly what you are thinking maybe not.
At service equipment grounded conductor and equipment grounding conductor are basically the same point, those connecting bus bars are a part of the grounded conductor bus assembly not a link between grounded and equipment grounding conductors.
The main or system bonding jumper (may be a wire, screw, strap, other metallic component tested/listed with the equipment it is part of, is essentially at the point where we do begin to segregate grounded and equipment grounding conductors.
Anything on the load side of the service disconnecting means enclosure needs the grounded conductor isolated from the equipment grounding conductor. The metal cabinet, metal raceways etc. load side of service disconnecting means enclosure (or first disconnect of a separately derived system) must be connected to equipment grounding conductors, and in most cases can actually be a part of the equipment grounding conductor - but you do not want those items carrying current of the grounded conductor so we do isolate them from grounded conductor so they don't become unintended parallel paths to the grounded conductor.