Your'e talking about the infamous ACD (All Channels Driven).
Yamaha is infamous for having the most stringent Circuit Protection in the industry. So when you try to force 5CH Driven, the Yamaha will LIMIT it's power output.
In reality, as you can read further on the topic, ACD does NOT happen in real life movie soundtracks. Otherwise, there would be a lot of AVRs across the world shutting down ALL THE TIME.
I think AI sucks, like 99% of all DSP modes.
I use the Yamaha AV Controller WiFi remote on my phone and iPad. It has a quick Speaker Level adjustment for the Center speaker (Dialogue Level) and the Subs. A lot of contents have bad dialogue soundtrack. You just have to increase the Dialogue Level manually as needed.