You're misinterpreting the Help Center information.
Firstly, 18.04 is offtopic as it is in development and not yet 'stable'. That's the first and foremost issue with the question you've linked.
We are also not a bug reporting site. Yes, we're here for developers' questions - more specifically, questions about developing on Ubuntu. But that doesn't extend to the reporting of actual bugs as questions, as those belong in bug reports, not Ask Ubuntu Q/A (especially since not all packages' developers actually pay attention here, and as Ask Ubuntu is not a discussion forum it's hard to add all the required developer troubleshooting information and such to a post, especially with the character limits on posts themselves).
Bug reports belong as their own bugs filed on Launchpad, and not as Ask Ubuntu question/answer posts. The post you linked to fits into this category as well.
If you don't like how this site operates with this policy, you're free to propose that the policy be changed here on meta in its own specific proposal thread, and the community-at-large is able to vote on that policy.