Not true! According to Apple.....
Types of DVD-R discs and where to get them
The SuperDrive in your Macintosh writes to 4.7 GB General Use DVD-R discs.
Use 2x or 4x media, depending on the speed of your SuperDrive. For best results, use Apple discs.
Note: A 2x SuperDrive writes to 4x media at 1x speed, so to get the highest performance from your 2x SuperDrive, use 2x DVD-R media.
For information on purchasing blank DVD-R discs, check the iDVD website or select the iDVD menu and choose Shop for iDVD Products.