No, the edge lighting is something else (the edge of the a51s can light up for notifications apparently based on the EdgeLightingManager). The ambient lighting is to prevent the screen from dimming/brightening based on the ambient light around them. Disabling "ambient display/lighting" should keep them at a constant brightness.
Bug 1777710 Comment 31 Edit History
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No, the edge lighting is something else (the edge of the a51s can light up for notifications apparently based on the EdgeLightingManager). The ambient display setting changes the screen brightness based on the ambient light around them. Disabling "ambient display/lighting" should keep them at a constant brightness.