You don't need to?
Yes, you do if you want that same optimization potential.
It is not "Highly customized".
The PS4 SOC IS punching above its weight significantly from comparable PC hardware. It is why most 3rd party devs aren't able to make a game that looks better than the first party games on the same system and even better on PC.
They are only able to make the game runs kinda bad on PS4 (in comparison to first-party titles) and then really well on PC. And that is because they have invested on a graphics architecture that has to just work reasonably well on a console while also working reasonably well on PC, and that results in PC always being better under those circumstances.
There is a reason why Quantum Break ran so poorly on PC, and that is because its engine was initially programmed to be highly optimized for the Xbox One hardware, and then the PC, in turn, had to run it in a very inefficient way.
I don't think you understand. It is the reality of the Windows OS and their graphics API's that are in the way of letting PC's utilize APU's the same way the console (not sure about Xbox's because they recently mandated all games be made for PC as well) API's make it possible. It is a question of design not processing power. If graphics engineers are able to pull off a certain feature for their engine by utilizing the highly unified structure of the console hardware, then they wouldn't be able to get the same performance on the equivalent PC hardware. Some features done in console games are simply not as efficient on PCs.
Not only that, but the mere reality of being able to work on a fixed platform where you can literally calculate all of your engine features in their best and worst case scenarios allows for developers to pick the exact techniques that are best for the hardware and also perfectly budget the performance of said hardware. Not possible on PC.
It is simply a fact. I mean the proof has been out there for a long time. Just look at the Sony first party games. They keep getting better and better looking as time goes on, on the same hardware. How else would this be possible?