Crank sensor is key, it is the only reference to TDC and...well crank position in general, even if it is only a crude 4 tooth wheel ( which identify each TDC...but the ecu cannot know which cylinder is which from this )

Phase sensor only identifies which is cylinder 1 for purposes of sequential injection.

As Cossie uses a dizzy.....phase sensor plays little role in ignition timing as cylinder ID is governed by the dizzy/rotor arm itself.