its not regarded as a show mead if there is nutrients added to it.
kens book is getting a little old, better start bugging him for an update version
adding nutrients turns a show mead into a traditional.
unless your entering competitions i do not see the point of doing a show mead. show off meads are just for showing off that you can do it without adding anything.
and yes they can ferment very well at the start, but they soon eat all the nutrient and go to a crawl, often producing bad tasting byproducts which can take years to age out.