i discussed this with a Friend of mine that worked for lexus he explained to me this is a Lexus option that can be turn on or off at the dealer with Tech scan tool.
I just purchased a very nice 2018 RX350 I notice while driving at night with my headlights on there is a dim light from under dash on the drivers and passengers floor if a shut off headlights that light goes out. This my be standard in the vehicle.