That is a really good strategy when splitting sections and on my forums we tend to only create a new related section when a topic in an existing one starts to dominate or become popular to a degree that warrants it.
However there are exceptions. And one of those can be for things that you want to encourage talk about.
For example we have an Introductions section on many of my forums - the number of threads in one is greater than a quarter of our members, on another it is just under a quarter. I’m pretty sure there would be much, much fewer introductions had we not had those sections.
Many times I have gone to post something here and thought that it may not be the kind of thing you want here because no section covers it or actively encourages it. In other words the categories set the stage.
On top of all that, ‘uncategorised’ has a negative feel to it - it suggests that you should try and stick to the other categories and only post uncategorised if you really have to.
I feel that you are missing out on interesting and valuable discussions by not having a general chat area to talk about anything related to discourse that doesn’t fit into any of the other sections. Members are also missing a place where they can network/make friends/get to know each other as well - the community is part of Discourse too.
Up to you of course, but I’d love to see you trial such a section for a few months just to see whether it works for you or not. (I think it will! :p)