It depends on what you mean. I don't train to hit people or targets; I train to hit a point in space. So if that space is 2 inches in front of the target, I hit it... if it's on the surface of the target, I hit it... if it's 2 inches behind the target, I hit it (assuming the target is yielding enough to allow me to do so). Whether the target is a focus pad, a heavy bag, or a person doesn't matter - it only matters where the point in space that I am aiming at happens to be at the time I'm aiming.
Think of a marble. Now hit the marble. Place the marble wherever you want it to be, and still hit the marble. I don't aim at people, pads or bags - I aim at a series of marbles that are available in front of, on the surface of, or within my target - how deep I go, or how much I miss by, depends on the purpose of the strike.
Here's an exercise for you. Get a partner. Practice hitting a focus pad with your partner with a particular technique until you can hit it reliably at the depth you desire, at the height of the person's solar plexus. Then remove the pad and hit your partner with exactly the same precision and power in the solar plexus. There is no difference... except the one in your mind, that tells you that you will hurt your partner if you miss - focus on the marble, not the surface behind it, and you will hit your target. Now change your target to your partner's nose. Again... there is no difference; your marble is still your marble, your focus point... but your mind will tell you it is different, because you can do more damage hitting someone in the nose than in the solar plexus, if you miss even a little - so don't miss! Hit your marble.
Focus is in your mind - it's all in where you place your marble, and how much you let your mind overrule your understanding of focus, how much you let the awareness of potential injury affect your ability to hit your marble. Now, I realize this is easier said than done - but once you understand that sparring is hitting a series of moving points (marbles) at the desired depth, you can move your marble closer to or farther away from any particular point, and once you can do that, you can hit as deep into your target as you need to for any conditions.