No, Dev target a specific performance level.First, you are comparing some fairly old architectures. Second, game developers understand that the trend is moving towards an 8 core mainstream, and will design upcoming games accordingly.
Still today, A 6 core CPU that have more single thread performance than a 8 core will have same or better gaming performance.
Core aren't slot that Dev fills to make their game. Think about it like a boss with a set of employee. Let say he have 6 incredible employee and another boss have 8 average employee. Both boss run a ghost writer shop and need to produce a 100k word book. (Aka A Frame for gaming)
There are two task, writing the words and at the end editing it. Editing would be done only by 1 staff to make it consistent. (It's the main thread in gaming that control and sync all the other)
Boss A 6 employee can write 1300 words per hours each and review at 5200 words pour hours
Boss B 8 employee can write 1000 words per hours and review at 4000 words per hours
so each boss need to start scheduling the work. He first assign all employee on the first hours into writing words
Boss A would be at 7800 words and Boss B would be at 8000 words.
Then one of the employee would start to review the text for editions,
For boss A, the 5 remaining employee would be done writing 11.8 hours later but they would have to wait for the reviewer. He would be done 19.23 hours later. (for a total time of 20.23 hours)
For boss B, the 7 remaining employee would be done writing 11.5 hours later but the editor would only be done 25 hours later (for a total of 26 hours.)
The fact that the boss B had more "Slot" to put the work into didn't mean they had the job done earlier.
Game work exactly that way. They are way more multithreaded than in the past, but there is still a main thread that is criticial. This is why gaming performance don't scale linearly. (Unlike rendering that have an almost linear scaling since all the job can be done by themselves).
What you need to think is there is by example for each frame x amount of CPU operation per seconds to do in the main thread, and there x amount of cpu operation to be done that can be multithreaded.
A faster core is able to do more operations per second. A really faster core can even do those one after another before the slower 2 core can complete them.
It still the case today, and it will be still the case in the future. Because game have to run a main core as fast as possible then spread the defined amount of load to other core. If faster core finish earlier, they can grab more work before a slower cpu with more core complete it's first job.
Again, in the current gen. 7600x 6 core beat all 8+ core from the previous generation. This is also why the E-core doesn't really help.
One of the gain right now of having a more core CPU is they are binned to run at higher clock. I would like to see what a 7600x running at the same frequency as the 7950x would do. I am pretty sure they would be very close.