Asus Rog PG278QR Gsync issue

My monitor has Gsync function with an indicator led which turns red as soon as the nvidia driver is loaded.
But when I deactivate Gsync in nvidia-settings it has no effect, the led stays red when it should turn white to indicate that Gsync is deactivated.

I did a test with windows 10 , the led changes color when I deactivate Gsync.