Yes the actuator arm should move a bit!
the Wastegate or the wastegate arm which connects to the actuator arm arent the failed parts. the failed part is the ACTUAL vacumm casing or actuator. the arm coming out of the actuator is perfect aswell. there should be some slack on it that u can move left to right. this isnt where the noise is coming from.
The problem is the actuators are failing, not moving the actuator ARM in and out enough. so when the actuator goes to push the arm or bring it in to open/close the waste gate, it doesnt fully close the wastegate. is stays open and the wastegate then flutters when off boost, since when on boost it closes it via force.
long story short, the actuator is at fault. nothing else.