P.S. I strongly doubt handwritten assembly is more efficient than modern C compilers.
As with everything, it all depends.
When writing super efficient assembly you write towards the destination and not necessarily to fit higher level language constructs. There are often ways to cut corners for aspects not needed, reduction in instructions and loops all based on well designed assembly.
The problem is you aren't going to do that for every single CPU instruction because it would take forever and not provide a good ROI. It is far more common to write 99% of your system code in C and then write just the parts that can really benefit from fine tuned assembly. And please note that unless you're writing for an RTOS or something crazy critical on efficiency, its going to be even less assembly.
Its not a misread, your interpretation skips the important parts. The problem with your interpretation is right here:
The knowledge is "of good and evil." Until eating they couldn't know that breaking a covenant was wrong no matter what their god has told them. They did not know that they should listen to what their god said, the concept of "should/shouldn't" was devoid of meaning to them. While they had free will, literally all actions were purposeless and the two would just bounce around the garden not knowing if they should actually listen to their god or not. This becomes more evident when you read further as well as look at the stories from neighboring cultures this was borrowed from.
Later in the chapter their god speaks to the other deities in the pantheon about how the humans must be cast out of the garden as having their new abilities, may find the tree of everlasting life and become as powerful as the rest of the gods and supernatural beings. The idea is that having knowledge of the ramifications of one's actions and living forever would mean that humans would no longer be controlled by the gods. That having free will, knowing what is good and what is evil and being immune to the wrath of the gods would render them all powerful.
This narrative then follows that their god casts them out into the world riddled with pain and suffering and humans eventually lose their knowledge of the past and how their god has their thumb on them. This is why Satan, "The Accusor", is called the bringer of light. As sin is defined as a transgression against god, Satan is there to show how the fall of man was truly an enslavement by their god. Rather than leave humans dumb bouncing around the garden or immune to suffering, their god keeps humans ensnared in this system of life, suffering and everlasting torment. the story of the garden is what makes their god relevant when they otherwise shouldn't be.