Pokémon Model Ripping Project

[fridge225]

This is with the DAE.
If you click twice where the axis is shown on my screen shots, you won't select the longer, more obvious RArm bone, but the RForeArm bone.
Try to rotate this and the whole arm freaks out and tries to rotate around the wrong axis.

This is FAR more noticeable when using the model in programs like Poser. (Pardon the image spam)

I see the problem. It is some strange weightings if you ask me. The bone Rhand is barely the hand at all and this causes the effects in your screenshots. This mostly due to rotating it by itself. A quick fix is to turn deforming off for that bone, or not use it and instead use RHandSub which is the bone that is actually weighted to the hand. That should ease some problems. But the main reason this occurs as RTB tried to explain is that these bones will deform like that unless moved in conjunction with the other bones. Meaning you can't just move RHand without it facing the same direction as RForearm. To rotate just the hand move the bone RhandSub. You can see this by configuring IK chains on the arm or just using auto IK, but then you have to make sure RHand is connected to Rforearm. And the ofcoarse the same for the left side but switched

tl;dr
That is how the bones are weighted. As RTB said you have to move every bone in the arm so it doesn't deform like that.