My apologies, I missed your replies. In your Spine project, you have a single slot called test which has two attachments, blue and white. The idle animation keys the blue attachment, so it becomes active when you playback idle. The action animation does not key any attachment, so it uses the attachment for the slot in setup pose. This is the expected behaviour in 4.1 (and I even think in 4.0).
Now, I've tried to locate the code you highlighted in your screenshot, but that's not what's found in the 4.1 branch in AnimationState.java on line 339. What runtime version are you using?
