How hybrid stop/start systems do it is irrelevant.
Hmm, not entirely.
I have a 2023 CX-5 Mild Hybrid.
In a mild hybrid, the i-Stop function doesn’t rely on the starter motor, but on the starter-generator, which is connected to the crankshaft via a belt. When the engine is running, the starter-generator charges the 24V lithium battery and, through a DC/DC converter, also charges the 12V EFB battery.
Restarting from i-Stop works the same way as in the non-mild hybrid version, except that it doesn’t use the starter motor (which is reserved for cold starts). Instead, it relies on the starter-generator powered by the 24V lithium battery. I assume the compression/spark ignition process remains the same.
During braking, the starter-generator recovers energy and charges the 24V lithium battery. When accelerating, it provides a small boost of power to the engine, making take-off from a standstill smoother and helps save a little fuel.
This applies to both manual and automatic transmission models.