If one actually looks at the letter of the EU directives, one sees
"2. Where the gross tonnage of a ship is less than 500,
Member States shall apply those requirements of a relevant
Convention which are applicable and shall, to the extent that
a Convention does not apply, take such action as may be
necessary to ensure that the ships concerned are not clearly
hazardous to safety, health or the environment. In applying
this paragraph, Member States shall be guided by Annex 1 to
the Paris MOU."
and most importantly in Article 3, item 4:
"4. Fishing vessels, warships, naval auxiliaries, wooden ships
of a primitive build, government ships used for non-commercial
purposes and pleasure yachts not engaged in trade shall be
excluded from the scope of this Directive."
The sail world article makes references to megayachts that fall under the IMO due to their size or usage.
Addendum : Here is the URL to the letter of the law:
http://eur-lex.europa.eu/LexUriServ/...57:0100:EN:PDF