"Combat accuracy" is a concept that is detrimental to a shooter's development in training, especially beginners. Many shooters espouse this type of "accuracy" and train using it as the marker. Throwing rounds as fast as you can without command of the weapon is useless. Run the gun...don't let the gun run you.
While training to become proficient and "one" with the gun, mastery of fundamentals is quintessential. Speed will come with proper training...it's inevitable...be patient.
Strive to get to a place in your training to be able to have tight groups at speed. Speed and accuracy are NOT mutually exclusive and can certainly coexist. Aspire to excellence. The ability to hit shots from 15-25 yards at speed is also crucial and will translate to faster and more accurate hits at close distances.
Shooting fast at three yards and hitting thoracic is not an art. When training, your groups should be as tight as possible (and continue getting tighter as time goes by coupled with speed), since they may/will open up when you're hit with an adrenaline dump. If you are merely in thoracic in training, you may miss the intended target completely when it counts most.
If your best during TRAINING is all over the place in thoracic and someone else's best is a tight group in the same exact time, the other person has an advantage in a defensive shooting scenario assuming both shooters have the same mindset, situational awareness and response to the threat time.
Many are fooling themselves or are being fooled into thinking that being all over the place in thoracic from 3 yards is a good gauge of proficiency while training. Aspire to be excellent and evolve.
Combat accuracy has it's place...in combat/defensive shootings...since adrenaline will probably dictate as such.