The layout is changed by setAlpha method, but the view hierarchy I got from Instruments has not changed

I am using Appium to test iOS app, but I think the problem is nothing to do with Appium.

The layout is changed by setAlpha method, our developer use it to show or hide a element(UILabel type), but the view hierarchy I got from Xcode-Instruments-Automation shows there is nothing changed in this subview.

Does anyone know how to solve this problem?
It will be better if there is a way to force Instruments to refresh the view hierarchy.