It's not only the plugin code itself being checked during the plugin acceptance review. Before the plugin is approved to land in the Plugins directory, some
boring formal aspects of its registration are checked as well. This includes things like meaningful description being provided, checking for source code repository URL or whether illustrative screenshots were attached to the plugin record. None of these aspects are really blocking the eventual plugin approval. If the maintainer explains clearly they can't provide such information, it's generally accepted. However, as pretty high standards have evolved for the items in our directory, having all the useful information filled in place can be considered as a sign of responsible attitude toward the ownership of the plugin.
To make these aspects of the review process more transparent and evident, a new feature has been implemented in the Plugins directory. New report called "Plugin check results" is now displayed to plugin maintainers together with the indication of the importance level and additional help on the issue. This new report can be seen as a complementary one to the existing Code validation report, that reports on issues checked and detected in the uploaded ZIP plugin package.
More information about the plugin initial review process can be found at http://docs.moodle.org/dev/Plugin_validation.