Earlier today, while stopped in line at a drive thru with the AC on, the ICE started due to a low SOC. In order to keep the car from "creeping", I put it in Neutral. As I did that, I noticed the arrows around the battery icon went from charging (up arrow) to discharging (down arrow. I thought that was strange, so I put it back in gear and the arrows showed that it was charging again. After doing this a few times and the arrows changing from charging to discharging based on if it was in gear or in Neutral, I figured it was just weird programming in the software, until I noticed there was a change in tone in the ICE each time the arrows changed. The rpms weren't changing but the sound was. I guess that was a difference in load on the ICE.
I'm guessing it doesn't charge in neutral because the load on the engine is "unacceptable" somehow, but, then why leave the engine running? I'm puzzled. Does anyone have an explanation for this?