How is a banana like a rugby ball?

A strange question, I know.  Bear with me here.

The European Court of Justice is considering a challenge to Norwegian company Stokke AS' trademark on the shape of their "Tripp Trapp" high chair.  Here's a picture of the chair:

Stokke's "Tripp Trapp" high chair

Nice, right? Classy.  Is the shape of the chair properly registrable as a mark?   It might be - remember, the purpose of a mark is to identify the source of a product or service.  In this instance, maybe the shape is so firmly associated with the Stokke chair that it could be properly registrable.  

In any event, Stokke registered the shape of the chair a trademark.  A Dutch court declared the mark invalid, but in a procedural move that I have to confess I don't really understand, the Dutch high court referred the case to the European Court of Justice for review.

The Advocate General, Maciej Szpunar, advises the Court, and has taken the position that the mark is invalid.

Maciej Szpunar

Now here's the interesting part.  According to this news release, Szpunar has apparently taken the position that 

A shape that cannot be trademarked is one "which results from the nature of the goods themselves or which gives substantial value to the goods," such as the shape of a banana or a rugby ball.

OK, so I understand the the banana - it's ... banana-shaped.  You couldn't register a banana shape as a mark for bananas.  It's generic.  But you could register the banana shape for some other non-banana-related product, like this:

Not a banana

Because the "nature of the goods" in this instance doesn't have anything to do with fruit.  Now, a rugby ball is different than a banana, at least in the sense that rugby balls don't grow on trees.
  

Does a rugby ball "derive its value" from its rugby-ball shape?  I suppose so. If it's not shaped like a rugby ball, it's not ... a rugby ball.  It's a soccer ball.  Or a football.  

Definitely not a banana.

But, again, why isn't it true that the shape of the rugby ball isn't registrable as a mark for rugby balls because it's generic - all rugby balls are shaped like ... rugby balls.