Brandt Snedeker played about 20+ practice rounds as an amateur when he had qualified for the Masters by winning the US Pub Links.
i did not know that!
It's my understanding that once you are in the field, you can play as often leading up to the tourny as you like. IIRC, past champions are considered honorary members and can play anytime the course is open.
Green Jacket = Membership
The club also took the privilege away from Bernhard Langer after he held up play for members. If you play it as practice, you better let the members play through.
A guy wins two green jackets and can't practice? With respect, that information sounds a bit suspect.