Microsoft, Nvidia, and AMD have made the claim about low-level APIs only when talking about low-level APIs, such as DX12, Vulkan, and Mantle.
Obviously an API designed for multiplatform use is not going to be as efficient as one solely dedicated to a single console, but Microsoft did not simply install Windows, DX12 and regular drivers on its console. They specifically mentioned further optimization to the hardware level, going so far as to have the custom firmware, drivers, and DX12 API tightly integrated leading to it being much more efficient then on PC. Words they have directly stated.
Seriously, get a grip, pointing out that DX12 is a low-level API with specific optimizations on the XSX does not make me MS PR. Take the console warring stick out of your ass and try to learn something. Not everything has to revolve around which console is better, you made a claim and I pointed out that it was inaccurate. The way you go on and on about Sony on this forum would have anybody here believe you are directly employed by them.
You still refuse to believe it, despite me posting numerous links to evidence to back my claim up, including something stated by a leading Microsoft engineer. I'm 100% confident that if somebody was to make a claim that goes directly against what Mark Cerny said, then you would jump on the chance to point out that they are wrong. But should someone dare try to point out something positive about Microsoft then they are obviously Microsoft PR and you obviously can't trust what Microsoft engineers have to say. It's like trying to debate with someone in a cult.