You are quoting from a sub-set of regs that apply to LUMINAIRES AND LIGHTING INSTALLATIONS, section 559.
559.1 Scope
This section applies to the selection and erection of luminaires and lighting installations intended to be part of the fixed installation
They do not apply to the fixed wiring. You are quoting out of context. The regulation allows for use of a socket to feed a light fitting and nothing else.
At each fixed lighting point one of the following shall be used for the termination of the wiring system:
etc...