I am not ignoring that it is a coaxial cable because it is not a co-axial cable -- the axis of the conductors is not consistent in a twisted pair with shield. Much of the benefit of a coax is the symmetrical arrangement of the shield w.r.t. the center conductor.
A shield around a twisted pair provide electrostatic shielding, but the question was RCA, and the two conductors (as noted by Kijanki) do not see the same electrical impedance which will defeat the benefit of twisting (at least for magnetic I/F) which works where both conductors see the same impedance hence induced voltages cancel. There is probably a reason why oscilloscopes probes, which are single ended, use coaxial cable and not shielded twisted pair.