When using Advanced mobile contributions, and VisualEditor mode, and pressing "Edit" at an section title, only that section becoms editable. In Desktop-version hitting "Edit", the whole article is editable, but the summary field is marked with the section number and input marker is placed at chosen section.
I like that feature with the desktopversion. With Wikitext I can understand you want to separate because it may be a lot of code.
Is this difference chosen on purpose?
Also it is not at all possible to get an full article editable, only either the intro or any section, rest of the article is not even shown. When clicking the very top "Edit" or "Edit source" only the intro becomes editable. So have VisualEditor or Wiki-code never worked.