There are two main directory listings of block related plugins.
- Plugins that are only blocks
- Plugins that contain blocks
A plugin can be listed in both, however there will be no benefit to your plugin SEO or ranking due to either. The only benefit to being a plugin that is only a block is that you gain the ability to be added to the Block Directory in the Block Editor itself, for immediate installation.
Block Only Plugins
Block Only plugins are plugins that only contain blocks.
Block Plugins are required to be much smaller and more minimalist than a regular WordPress plugin in order to be safely installed with a single click. That means as well as keeping to the regular plugin guidelines you’ll also need to follow some additional rules. In particular, you should stick to mostly JavaScript code and keep PHP to the bare minimum; and not add any UI or other code outside of the Gutenberg editor.
If you’re a committer of a block plugin that does meet the criteria for adding it to the Block Directory as confirmed by the Checker tool, you can then add it yourself using the Block Checker tool: