To be clear, AMD has much less performance loss if any. In some cases surpassing the performance in Windows on those same games.
So is it the game's fault? Mostly no. The performance gap is not due to poorly written games, it's about:
- how efficiently DX12 gets translated to Vulkan
- how optimized the Vulkan driver is for gaming
- how much driver-level work is done per platform
Games that are poorly optimized on Windows will also mostly likely perform badly on Linux.