When you dig into those data more,

you can easily find that those top 3 pointer teams all shot more 2 pointers than 3. Why? Because it has to be balanced, so you can "surprise" others to get a brief opening to launch your shot. 3 pointers, has a natural lower percentage than 2 pointers. Considering defense, it's even more difficult, if you ONLY shoot 3s.

Your whole theory is based on the assumption one only shoots 3, one only shoots 2. Once you miss, you get your offensive rebounds, and you go back to the 3 pointer line again to launch another 3. Let's put it aside, whether it's possible. Let's just assume nobody gets any offensive rebounds, with 33% and 50%, and same amount of shot attempts, you get same score all the time.

Now, let's look at it beyond the numbers. Yao, TD, and Amare, three among the best inside scorers, Redd, Allen, and Dirk, three among best 3 pointer shooters. When you know for sure first 3 guys are going to shoot inside the paint, and latter 3 guys are going to shoot 3 for sure, you defend them hard. I am pretty sure first 3 guys would still be around 50%, but 3 poiner shooters would be much less than 33%. Do you agree?

Let's look at Dallas' 0.395 3 point shooting percentage. Can they say we are shooting nearly 40% beyong the arc anyways, why don't we just launch 3s in our own back court, there is no defense, and that is 3 pointer. Do you still think they can hit that 39.5%?

They are good shooters, and they are smart about their shots selection, that's how they got their high percentage. Not as you suggested reversed, that they have high percentage shooting, they just should shoot all 3s.

That's why the whole NBA has been working on it consistently around the topic, how to get high percentage shots. It has less to do with team shooting percentage, but rather depends on the shot iteself. The closer to the basket, the opener, the higher is the percentage.

Balanced, is the key word. If you can only drive, but no jump shots, people only need to defend your penertration, without honoring your long shots, vice versa.