Topic on Forum:Wiki Talk
This is a permanent link to the first version of this post.
You can view later versions on the post history page.
I think you might be able to argue that, on pages where there are more information provided by demographic lines, characters are more developed and you have more information about the characters, so you can write a longer description with more tropes. Therefore, if a character has a large demographic listing it should have a large description.
However, I think this is going to be a "reality does not match expectations" thing. I wouldn't rely on this coming true on every page. Even if some cool information isn't included on the infobox, you can always include it in the description.
Agree with your decision. Let's "freeze" the fields until someone has a good point.