Agreed, the centre junction of the radials is not always at 0V. Current
flows along the coax braid on the inside, meaning that the inside part of
the coax braid and radials junction can be any voltage. The radials have a
voltage gradient along them because of the standing wave. Because the return
current flows on the inside of the coax braid, it is normally safe to touch
or go near the outside of the braid. For permanent low installations in a
public area, coax should be used instead of twin feeder. The fact that the
return current flows on the inside of the braid gives coax its shielding
properties.