That's not exactly what 314.3 Exception 1 says. It just says you have to provide internal bonding means, not that you need to use them. Whether you need to use them is determined by the Article 250 requirements.
Simple example would be EMT (no wire-type EGC) dead ending into a non-metallic device box with a device that has no EGC connection. So there's no bonding connection to be made within that box. Perhaps 314.3 Exception 1 still means you have to put a bonding bushing on the EMT connector, but nothing gets connected to it.
Cheers, Wayne
Code aside here is my interpretation of the physics, which may be way off base, and also keep in mind terminating metal raceways on non-metallic enclosures is not super common, possibly more common with equipment.
Ferrous metal raceways should be able to serve as complete equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, and they need to be electrically continuous as a ground fault path.
Attaching each end of the raceway that terminates on a non metallic enclosure to an equipment grounding conductor ensures the raceway is in parallel with the fault clearing current. Each metal raceway still needs the capacity to conduct safely any fault current likely to be imposed on it, supplemental EGC or not.
If both ends of the metallic raceway are terminated on non-metallic enclosures a bond bushing (or bonding means) in each enclosure, not just one end, and attached to the other equipment ground present in that enclosure ensures the raceway is a fault clearing path.
If only one nonmetallic enclosure is present a bond bushing (or other bonding means) located in the non metallic enclosure and attached to the other equipment grounding conductors in that enclosure ensures the raceway is a fault clearing path.
If there is no supplemental equipment grounding conductor in the raceway, then the raceway still needs to be attached to the other equipment grounding conductors in each non metallic enclosure to ensure the raceway is a fault clearing path.
If there is a supplemental equipment grounding conductor in the metallic raceway not attached (bonded) at both ends by some means (no parallel path) then the supplemental equipment grounding conductor is enclosed within a ferrous metal conduit that has a magnetic field surrounding the conductor. And during a large fault say to clear a inverse time breaker, it induces a current in the conduit itself. This induced current creates a counter-electromotive force (CEMF), acting as a form of "choke" or inductance, that opposes the flow of the original current. reducing the EGC's ability to safely carry fault current from what it would be if it were a parallel path.
