You are correct on the vvt part of it.

The cam sensor reports to the ECU the actual cam position, the ECU then has confirmation that the cam has advanced.

the cam sensors main function actually is to time the injector sequence so the engine can run one injector at a time rather than batch or group (like starting).

This same stumble happens in other cars too if the cam position signal is missing. There will be spark and fuel but not at the precise moment as the ecu has 1 in 6 chances to time the firing correctly for a 6 cyl engine, If the engine is ancient group or batch fire you will see no change (there would usually be no cam sensor in those either - like ancient GM or toyota/daihatsu)

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)