What does me needing to make games has anything to do with what I'm saying. Do you make games?
Tell me why Requiem was designed for Series S and only performs at 30FPS and why I can play at larger than 60FPS and have native 4k renders on my PC? If Requiem was designed for Series S, the PC version should look and play like the next-gen consoles.
So now you are going to educate me on what I do for a living? So what code path does the Series S use that's not available on the PC? Are you saying there are different versions of the same graphics engine? Have you ever setup a graphics state machine in DX/OpenGL? Tell me how that would look.
According to you, the game was coded for the Series S. That's DX. So why are you mentioning the PS5's OS?
No according to me console game development is held by Series S.
Each platform has it own code path no matter if PC or consoles and developers have to make concessions in what they do due the limitation of lower hardware... in console space it is the Series S... in PC space is the minimum spec choose but the developer. You should be playing it at 120fps or more on PC with your beef PC... the fact it is just reaching 60fps already tells you the game is being held by lower hardware.
And yes... my mammography in University was about game development and yes I had to code it to understand how Drivers, APIs, Engines, etc works to write and defense my project.
Each of these APIs you say it is all equal have different code path for different platforms, hardware, vendors, etc inside... it is called abstraction level.... when you call a function in DirectX internally the function has IFs for each platform, hardware type, version, etc... and no Series X code is not the same as Series S... just because the SDK or Engine makes you believe it is the same doesn't mean that internally MS coders deals with it for you.
The same for Unreal Engine that has code specific for all platforms that it support.
Same for the Tools you are using to whatever you work.
Same for Windows, Linux or Mac.
PC development is based in abstraction layers with specific code for each hardware.
The nVidia and AMD drivers are full of IFs for each single specific GPU they launched... sometime a code works for a family... others for a version of a GPU inside a family and there are cases where specific code are posted to a single specific GPU.
Epic Unreal Engine developer has a lot of docs of how they deal with different code path inside they engine... because a code that works well some GPUs of AMD won't work well on nVidia or others AMD GPUs... so they have to make the best and optimized code path for each either group or single hardware.
You won't find any single example of code that talks with hardware that doesn't have specific lines of codes (or even files with codes) for each different hardware... including hardware versions of the same arch/vendor.