Looks like we can't reproduce the issue or there's a problem in the test case provided.
When we move any object on z on Sencha Animator interface, it doesnt represent the real perspective, just when we export. It should get smaller or bigger depending on the position z value.
Per example I had an object as background and another object rotating 360 in y.
On sencha animator interface everything looked fine, but when I exported they were intercepting each other. So I moved the background on z to avoid the interception, but visually nothing changed.
It should get smaller.