This looks a subpart of T286137: Fix alignment of special pages in 2021 vector.

It may be a subpart, if both where moving in the same way. But may the decission be that taking the full width is not what we need. Or another solution (like just riding apart from the "Special" or "Category" tab there and moving elsewhere. The behaviour here is important, as they are the only pages where full width is achieved if the sidebar is collapsed.

Change 744842 had a related patch set uploaded (by Jdlrobson; author: Jdlrobson):

[mediawiki/skins/Vector@master] [Documentation] Document decision in T293441 in code

https://gerrit.wikimedia.org/r/744842

Change 744842 merged by jenkins-bot:

[mediawiki/skins/Vector@master] [Documentation] Document decision in T293441 in code

https://gerrit.wikimedia.org/r/744842

Yes @alexhollender, that explains why the design is not going to be consistent. I'm not going to argue about the importance of consistency. The issue wasn't about the fixed or full width, but about the tabs in the upside not moving with the design. If the sidebar is collapsed, the content is moved to full-width but the tabs are fixed. And, besides of design consistency, this is the error I was reporting.

@Theklan as the project progresses the layout will continue to change. We may end up with something like this:

Anyways, I don't see the purpose of us discussing this since you will continue to tell me that I am wrong and don't know what I am doing.

The tab solution seems pretty good in this mockup, and solves the problem presented here, indeed.