The title is about it. But, specifically there is a bug (https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1227365) which causes no grub menu to appear on loading (even holding down shift). I fixed the problem by running boot-repair. I just wish someone had told me before I had to do a complete reinstall since I couldn't log in in recovery mode...
Is it reasonable to warn people about a bug and provide a workaround in the main site? Yes and no, to some extent.
If there is a question asked about this bug, then you can answer the question, stating the bug link and that there is a work around. However, it may be more prudent to state that in the comments of the question instead of an answer, because the question is likely to be closed as a bug report.
However, if you are going to post with the intention of making the public aware of the bug, then you have to be very careful of how you word this. You need to create a question asking about the symptoms of the issue, then answer your own question with the link to the bug, and also the workaround.
Otherwise you should not do anything except (1) wait for the bug to be fixed, and (2) only answer questions which match this bug issue with the bug link and the workaround.