1 inch punch question?

It actually goes right back to Wing Chun. The point of impact is the knuckle on the ring and pinky finger. It aligns those knuckles with the ulna or lager bone in the forearm. And it also is a smaller point of contact compared to a traditional western style fist. Smaller point means more damage.

Without proper training you will get whats called a boxers break. It takes years of training to actually build that structure strong enough to resist breaking. With all the info given this is also the reason why it is a vertical fist compared to a horizontal one.

It all comes down to bone and joint alignment.

Also that little flick at point of impact will drive that knuckle deeper into the target.

Same principle is applied to the 3 inch power punch as well.

It works great in close quarters compared to traditional punches. And in reality all you need to hit someone and inflict damage is a couple inches. It is another reason why this punch is popular in certain martial art circles.

You're not flicking your wrist upwards. If you were holding a spatula and trying to flick something on it towards your face, that's the wrong kind of exertion.

You should be pushing the energy outward through your pinky and ring knuckles. Imagine holding the spatula in reverse-knife grip and trying to flick food forward in front of you. Or holding a mini hand shovel in a reverse grip and scraping dirt away from you.

This creates a natural energy that aligns with extending your arms out. Try doing a close pushup (the kind where your elbows are tucked in, not in eagle spread form). At pushing up, try the difference between pushing with your pinky and ring knuckles vs pushing yourself up with the top two knuckles. At extension, tuck in your elbows closer to your ribs and see how it's easier to rest.

You want that kind of structure where all energy and power is mostly from your structure as you apply it in the attack.