Uh... wow. You have little idea how modern vehicle electronics or system controls work.
The alternator is supposed to output a steady nominal 12V (in actuality, soemwhere around 13.8-14.5 to charge the battery and run all the systems in the car at the same time.) 5V would not run the car’s electrics, let alone electronics. 5V is provided to the sensors and only the sensors via voltage conversion in the car’s computer module - however, not all cars use a 5V baseline and many use 12V instead. One reason 5V is used is because this was inherited from the computer industry - your typical desktop computer of the 1980s had a power supply that provided 12V and 5V for various technical reasons and with the addition of 3.3V this continues through today.
> “The alternator is supposed to output a steady nominal 12V”
I know that but it is stepped down for electronics to 5V. When I wrote that the 5V comes from the alternator, I didn’t write it was stepped down from 12V because I wanted to be short and didn’t think it was necessary to insert detail.
Electrical and Electronics are separated by scale. Of course, car electrical components operate at 12V and electronics have had a 5V supply for impedance matching. Impedance matching is the reason why there’s a lower voltage norm.
Electronics can be fried easily if voltage swings. I know the onboard computer control modules have voltage regulators built into their input or on the circuit card. They will never rely on a higher voltage alternator which can degrade with time.
But you miss the bigger point as you think you’re somehow so knowledgeable about the minutiae.
Do you know what the bigger point is?
No, I don’t think so, You’re too hung up with drawing attention to yourself lecturing on distractive details.