BobDole gave the most accurate answer here for how testing works that I saw. All of the specific skill (mechanical, electrical etc) based questions are just used for checking whether you would be proficient for a particular role. Your AFQT score is the "actual" score people will refer to when you say what you scored on the ASVAB. So you can miss all the electrical questions and still score a 99 essentially, so long as you get all the reading and math questions right.
BobDole gave the most accurate answer here for how testing works that I saw. All of the specific skill (mechanical, electrical etc) based questions are just used for checking whether you would be proficient for a particular role. Your AFQT score is the "actual" score people will refer to when you say what you scored on the ASVAB. So you can miss all the electrical questions and still score a 99 essentially, so long as you get all the reading and math questions right.