I think the distinction you made is accurate:
There are indeed topics that fit in multiple categories, which makes things difficult. Ideally categories worked more like tags, such that multiple categories could be attached to one topic…
The Go variants category could indeed be a subcategory of the General Go Discussion category, but I thought the latter wasn’t supposed to have subcategories; it’s a catch-all category for topics about Go that don’t fit in one of the other more specific Go-related categories. For example, tournaments or teaching or strategy topics all also would fit as subcategories of the general category.
I think this would be polite, but not inherently necessary. I’m sure everybody here has good intentions. I’m not
If I were to categorise the how-to and game topics of the Democratic Go game, then I’d put the how-to in the Go variants category, since Democratic Go is basically a Go variant (like Rengo, or Zengo, or Team Go) and I’d put the game itself in the Forum Games category, since the topic is a game played on the forum.