Hmm, that’s a good question. I don’t think that is the only difference. In my opinion, the technique you’re executing has a few different aspects. If I’m going to strike with seiken, my technique will be overall completely different than let’s say, ippon ken. My power, wrist structure, target, and overall technique will be different. Even using koshi can be different depending on the variation of technique I’m using. Sure, in essence, it’s still a punch, but it definitely makes a difference in how I execute the technique. The same principle can be applied if I was kicking with the toe vs. the ball of my foot.
This is a broad question with a very specific answer in my part, but I feel like that can be applied to any technique in karate.