If you browse the photo albums posted under the old website and search either for Megasquirt or some of my albums, you’ll see similar solutions to those already proposed.
The Denso system runs its fuel either semi-sequentially - it pairs 3B/5B, 2A/4A, 1B/4B, 3A/6A, 2B/6B and 1A with 5A or fires all twelve at once (during startup?). This is why it’ll start without a cam sensor or run after the cam sensor gets subsequently disconnected. The pairing choice does let it set the fueling differently on each bank (each bank has its own MAP sensor). The cam sensor is thus used to tell it which bank it is fuelling and adjust each bank’s fuelling accordingly if an O2 or MAP sensor tells it to.
The cam sensor is there also for OBD2 compatibility as the ECU has to detect misfires and diagnose which cylinder is at fault. It can only do that last function and maintain OBD2 compatibility with a working cam sensor as it won’t know which bank is firing otherwise.
Aside from OBD2, the Megasquirt is a more sophisticated setup.