Why does Qiskit swap gate accept registers, but cswap doesn't?

Question

In Qiskit, I am trying to perform controlled-Swap (cswap) of two registers, but an error occurs:

from qiskit import QuantumCircuit, ClassicalRegister, QuantumRegister
from qiskit import execute, IBMQ, Aer

c = ClassicalRegister(1)
ancilla = QuantumRegister( 1 )
phi = QuantumRegister(4, 'phi')
psi = QuantumRegister(4, 'psi')
qc = QuantumCircuit(ancilla, phi, psi, c)
qc.h(ancilla)
qc.swap(phi, psi)
qc.cswap(ancilla[0], phi, psi)

The swap works, exchanging each qubit of the first register (phi) with each qubit of the second register (psi), I expected that the cswap would work in the same way but the following error occurs:

qiskit.qiskiterror.QiskitError: "QuantumRegister(4, 'phi') is not a tuple.A qubit should be formated as a tuple."

I have read this answer but it didn't help

Answer 1

I don't know if this is what y'd like to do. But I think it's because ancilia does not correspond to the quantum bits that follow

qc.cswap(ancilla, phi, psi)
qc.draw()