Thank you for the replies guys. Totally understand that there will be many reasons behind different operator's "policies", but I was curious if this nav light on during daylight is a regulatory requirements in any part of the world.
I'm fine when people have their nav lights on during the day, but I was queried by an engineer in Indonesia when I had mine off during the day despite Indonesian CASR clearly says nav light on during sunset to sunrise, which further confuses me.
I'm flying the A320, if its powered on by APU, you will hear the APU, no need nav light to tell you. If it runs solely on battery the nav light will probably not be illuminated (aka shed) anyway, so I can't understand the "navlight-indicates-powered-on" argument. ✌️