The categories curation in Openbase includes a category, but also a framework. So as you mentioned, under Table libraries, you could have React, Vue, Svelte libraries etc.
We currently filter those by framework, but unfortunately, we didn't have the time to fully implement this page prior to the launch.
What should be in this page is a dropdown where you can choose from 10 different frameworks, and see the results for that specific framework. That dropdown, along with the URL routing to support it, is still missing from the product. It's one of the most important things on our roadmap, so expect to see it on Openbase soon.
Unfortunately, there's no way to 100% ensure all packages are included inside a category since the curation is manual, but I would say we do base it on extensive Google/npm/GitHub search. In the future, we want to involve the community in the curation process, so anyone can suggest new packages for a category or categories to a package. Not a simple thing to implement, but we chose this challenge since we do feel that categorization can provide a lot of value.