No - that's not 'polarised', but 'balanced' to 'unbalanced' - a different thing altogether.

It is normal practice to connect the screen to the 'cold' conductor at only one end to prevent earth loop hum.

A balanced line has a twisted pair carrying the 'hot' (phase) and 'cold' (antiphase) signal, and the screen is the reference point for the 'balanced' signal.

The twisted pair reduces induced noise through 'common mod rejection' - the noise gets into the signal, but is rejected because it is 180° out of phase with itself, thus effectively being cancelled out. The technology is borrowed from telephony, which is why we still refer to a signal as 'line level' (0.775v at 0dB).

For some strange reason, guitars are rarely balanced even though it is now the norm with microphones and mixers.

I'm sorry if my attempt to simplify this into 'lay terms' offends purists, but it's nearly right!!