I am going to take issue with the theory that closed loop only targets stoic... I understand that the fuel table doesn't control the target AFR, but somewhere in the code there is a target average 02 voltage that the ECU is trying to achieve via STFT. That target varies with load and temperature. The ECU is fully capable of targeting and maintaining closed loop operation between mid 15s and low 13s before it reaches the limit of it's range and drops into open loop.
My best example that can easily be observed would be the warm up phase... Watch when it goes into closed loop, and what the AFR is doing as it warms up.
You can also see it driving with a light load that's not enough to force open loop. The AFR will start to go rich, and it's still in closed loop.

