He is saying that enabling the "Smart Return-to-Home" feature in DJI GO (see the screenshot below) will trigger "Low Battery RTH" (as documented in the "Return-to-Home (RTH)" section of the Mavic manual).
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However, the "Smart Return-to-Home" feature is not the same thing as "Smart RTH" (as documented in the "Return-to-Home (RTH)" section of the Mavic manual). In fact, the "Smart Return-to-Home" feature is not mentioned anywhere in the Mavic manual. The manual is written in such a way that would make a user think Low Battery RTH is always enabled (and cannot be disabled).
So, Smart RTH allows for obstacle avoidance and Smart Return-to-Home is for low battery? After having issues with the Phantom 4 sensor and the sun, there is absolutely no way I want the avoidance sensors active while in RTH. Last thing I need is for me to somehow lose control and the drone just sits there because it mistakes the sun for a threat.