IK Constraints works differently due to its creation order

Hi, during handling a character's arm with IK, I found out that IK creation order affects its behaviour.

Here's a simple test.

IKs of Upper bones are created from outer to inner.

IKs of Bottom bones are create from inner to outer.

Here's how those two arms work :

Normally we expect the behaviour below... I spent a day figuring out this. What's going on behind this?

Have you tried changing the order of the constraints? You can drag and drop to change the order they're applied.

Wow, ok, didn't realized the constraint order affects this. Thanks for the answer.