My experience has been different. I find that not needing to have hyper-focus for extended periods of time with constant micro-adjustments has a big effect on fatigue - especially on long trips. Not needing to touch the wheel while using gaze-detection for attention tracking just reduces the annoyance IMO.

I find it very similar to operating an airplane with a reliable autopilot. The GFC-700 is super good at what it does. But it is still on me to monitor what it is doing, while at the same time significantly reducing my workload.