I haven't found "Chill" mode to be a useful tool for increasing efficiency and there is no indication it's designed for that purpose.
From what I can tell by experimenting with Chill Mode is that it re-maps the throttle response and adds a slight delay to soften the reaction and make it resemble an ICE car with a torque converter. I think it was designed to help people who were set in their ways become more comfortable with the instant throttle response of an EV. If anything, it's probably counter-productive to efficiency because humans have an amazing ability and tendency to adapt to such things by unconsciously pushing the throttle deeper to get the desired response. I think Standard Mode for acceleration, with it's more crisp and accurate throttle response, will typically return the best efficiency in normal driving.
I can see how this might assist someone who has an old ankle injury or can't move their ankle through a normal range of motion but anyone with normal ankle mobility is probably best served by Standard Mode on the accelerator.