I agree that most people wouldn't know how to create biofuel, or properly connect generators. You may or may not be surprised at how many people can't change a tire or jumpstart a car. However, the same can be said for a great deal of what is already in game, like loading/using a firearm, farming, combatting crop diseases, building functional animal traps, performing basic firearm maintenance and repairs, properly attaching weapon mods, carpentry, etc. Like you said, gameplay will often trump realism, though skillbooks can be a justification for any in-game knowledge. Also, depending on what jobs are added in the future, you could argue that they absolutely would have the knowledge in question. Whatever the devs go with will be an interesting addition, and I have faith that the modding community will fill in any gaps they think need addressing.