There is overhead but Vulkan allows you to batch draw calls in a far more efficient manner. It can also generally use multi threading to feed a GPU even if the game isn’t coded with that in mind. Basically Vulkan offers so many improvements to efficiency and parallelization that the overhead is a drop in the bucket compared to the overall speedup in draw call optimization alone.

It has nothing to do with the answer being wrong, it’s how you get there. If you fail to subtract seven, realize your mistake, and correct it you have already passed the test. People with dementia will either start to count down by the wrong amount, start counting up, stuff like that. You are testing whether they can abstract verbal instructions and maintain a consistent train of thought while performing trivial calculations.

Counting down on your fingers one by one and only saying every seventh number would be considered a perfect score once you make it to about 63 if you don’t lose track of what you are doing or start forgetting numbers.

Having more than one emulator available is good for people trying to get into development. It is still common to guide newer developers toward writing their own emulator for a very well understood system to gain an understanding of some of the more high-level concepts and abstraction. Having multiple different codebases gives you ideas on how to implement features in new ways.

Of course, the cynic in me says it doesn’t matter if the products aren’t competing in feature sets, the more robust system will be used and developed, but I don’t think that’s the point of the exercise.