No, you still got it wrong:
1. 'n' fragments are generated for a triangle without backface culling.
2. 'n' fragments are generated for a triangle with backface culling if the triangle is determined to be front facing.
3. '0' fragments are generated for a triangle with backface culling if the triangle is determined to be back facing.
You never ever get two faces being rasterized for a single incoming triangle.
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