I read the details of Shor's algorithm implementation at the link https://qiskit.org/textbook/ch-algorithms/shor.html#2.-The-Solution and had a question. As a concept, when Unitary is applied with a Control Qubit, because of Phase kickback, the Phase gets applied to Control Qubit instead of the target register. So, that means there should not be any impact of the Unitary operator on the target register. But in Shor's algorithm application, we see that the impact is seen in both the Control bit and the target register. If we measure the target Qubit, we see the superposition of 1, 2, 4 and 8 (for the example taken as Qiskit implementation) along with impact Phase rotations in Control register too.
Is my understanding correct? Have tried a lot to search and get information on this but could not find. So, can someone please help me understand this?