A movement is a change of position over time, no matter if it was interpolated or not. To detect movement (such change) you should compare current position with position stored in previous process step.
var object : Node2D
var old_pos : Vector2 = object.position
func _process(delta: float) -> void:
if old_pos != object.position:
old_pos = object.position
Please note, with such comparison you should take in account
float precision errors.