Knowledgebase Article Permissions

Hi,

Goal- I want knowledgebase articles in the Category 'General' to be available to 'Registered Users' but not to public.

This article

https://help.zoho.com/portal/en/kb/desk/self-service/knowledge-base/articles/organizing-your-knowledge-base-content#1_None

Seems to infer that it either isn't possible, or that it can be done by setting the Category to 'Groups'

'2) Groups

Categories with a group visibility setting are accessible only to certain user groups. The articles created under this category are accessible only to registered users.'

But this doesn't work- a Registered User who is not part of a Group that's tagged here does NOT get access to the articles. so how do I achieve this please-

I want knowledgebase articles in the Category 'General' to be available to 'Registered Users' but not to public.