To say it's a skills test is 'biggin it up' a tad.
If the rating has expired, its called a Skill Test leading to a Renewal; if the rating is still valid, its called a Proficiency Check leading to a Revalidation, a simple case of definitions. In either case the test has the same content, and should not be confused with a PPL initial issue Skill Test which is much more comprehensive and is not repeated once passed.
There are clearly a number of options with ORS4 No 711 to allow a NPPL medical to be used however that poses certain revalidation problems where, if your licence contains an SEP rating, only the CAA can change it to a SSEA rating not the examiner. It appears that nobody has considered the revalidation process, or if they have, they have forgotten to tell the examiners how to go about it! An examiner is only authorised to sign up what appears in Part XII of the licence.