The ALS does not adjust automatically when the end user adjusts the display brightness to 0%.
This issue was discovered on the XPS 13 9300 and XPS 13 7390 2-in-1 with FHD configuration. End users may suspect the ALS is not working properly.
Not Applicable
Microsoft has confirmed this is working as per designed. On FHD devices, the brightness is controlled using lux level. When the brightness slider is set at 0%, the brightness always stays at 0% no matter the environment lux change. Also, the slider will represent the auto brightness bias, and this is why there is no brightness changes from 0% slider after manually setting the brightness to the lowest level.