Chi Sao with sifu

[Wayfaring]

To me Chi Sau is training on how to deal with energy.
In some cases you can control the opponents centerline without controlling their hands.

I would agree. Over-emphasizing controlling the hands leads to chasing hands, which leads to losing centerline control. If your huen sao has more to do with sticking to your opponent than it does to do with recovering your centerline you see this.