There should be no hard rules in bonsai. Every tree is distinctly different from another hence different rules should apply.
In competitions, one judge may favor one entry but another may disagree with him.
In fact, strict adherence to rules will likely hamper the imagination of the artist, limit his creativity, and prevent him from creating a unique masterpiece which carries with it his own brand of originality.
Worst, his collection may just be miserable imitations from books or with formulaic look as if mass produced with a moulding machine.