Single conductor shielded cable used to be common, but maybe, not so much now.
That "single" conductor is not concentric with the shield, as in coaxial cable, & the cable's impedance is not well specified..
Well, it is loosely concentric but with very loose tolerance.
I remember, decades ago, when I was more into radio and was always messing with microphones that I could only get single conductor shielded cable which was a problem because I needed a second conductor for the PTT pushbutton. You could buy twin shielded cables for stereo audio but not two wires with a single shield. Whenever I found that cable I would buy it.
That kind of shielded cable is fine for audio and relatively low frequencies but no good for RF. In fact, one of the oscilloscope cables I have is plain, very thin, shielded cable and it works fine at low frequencies.