In the PAST, the official Airbus position was feet completely on the pedals. This is the way I fly almost every aircraft of any make or size.
A few years ago Airbus surveyed their pilots on what technique they use and found a perfect 50/50 split between the 2 techniques. There was no correlation in experience or background to one of the two techniques. Civilian/military, test pilots/airline pilots, all groups had both techniques. So the official Airbus instructor position is now to do what works for you.
I will always advocate for entire feet on pedals, but anyone saying that one technique is incorrect is ... incorrect, and pedalling outdated information.
Reference is the Airbus Worldwide Instructor News app.