Yes, it does, and it's not a fixed sampling pattern. ATi is not a lier.
16x 6xRGMS FSAA - R300 (Quality Mode)
16x 6xRGSS FSAA - R200 (Quality Mode)
Here are some comparable pictures:
2x FSAA-P - R300
2x FSAA-P - R200
2x FSAA-Q - R300
2x FSAA-Q - R200
4x FSAA-P - R300
4x FSAA-P - R200
4x FSAA-Q - R300
4x FSAA-Q - R200
6x FSAA-P - R300
6x FSAA-P - R200
6x FSAA-Q - R300
6x FSAA-Q - R200
16x 6xRGMS FSAA - R300 (Quality Mode)
16x 6xRGSS FSAA - R200 (Quality Mode)
Here are some comparable pictures:
2x FSAA-P - R300
2x FSAA-P - R200
2x FSAA-Q - R300
2x FSAA-Q - R200
4x FSAA-P - R300
4x FSAA-P - R200
4x FSAA-Q - R300
4x FSAA-Q - R200
6x FSAA-P - R300
6x FSAA-P - R200
6x FSAA-Q - R300
6x FSAA-Q - R200