I think if a general category is closely related to child categories, then it makes sense to add a setting to apply a channel to all child categories. That is, to have a common chat for the entire section.
For example, if we have a thousand categories in total, then we will have 50 channels, not 1000 channels. On more general channels, users will communicate more actically than on 1000 channels. Most likely, they will not have anyone to communicate with!