There has been no AMD GE game that required official patches to massively improve a performance deficit for NV GPUs. Thus, AMD's GE program & devs who sign on to it, are not actively gimping NV hardware during development.
The few examples in which NV ran poorly on release: Dirt 3 (Global Illumination) and Tomb Raider was resolved by NV themselves with an optimized driver which massively boosted performance.
Anyone remember Deus Ex: HR? It was one of the first showcase title for AMD GE, ran excellent on NV hardware on release. That has been the norm, and games that ran poorly were the exception. Every single NV GameWorks title has ran poorly on AMD and indeed, they all have official game patches to improve AMD performance a few months later (months, not days).