My strix 6900 xt has an aio but the fans stop and go even after playing for a while when they should be running all the time. Never had a gpu with an aio before so not sure if this is normal.
Honestly don't know much about the card, was just looking at a review for it. The guy does mention at one points a fan not running very often (ie it's not needed at that moment so it doesn't run)
But have you checked the settings for the fans on it etc, it looks like it has an asus app that you can control the fans with (the guy in the linked video shows it around the 8min mark.
Depending on how you have the fans set it could be set to stay off until it hits a certin temp similar to the 'zero rpm' feature for gpu fan curves in the radeon software.
Maybe OP should also ask on the Asus forum, other owners of the card could offer more insight.