As mentioned at the Teahouse (https://en.wikipedia.org/w/index.php?title=Wikipedia:Teahouse&oldid=991606142#Seeing_wikilnks_to_subtitles_on_my_iPhone), and after doing some testing on my own devices, it appears that section links do not properly navigate to article sections using the Wikipedia app on either iPhones or iPads. I can successfully navigate to the desired section using Safari, in both mobile and desktop views, by clicking on the link, but not in the Wikipedia app; it merely navigates to the top of the article. I put several section links in my sandbox to test in various formats; all work in Safari (both modes), none work in the Wikipedia app beyond sending me to the proper article.
I am using version 6.7.3 (1789) of the Wikipedia app on an iPhone X and an iPad Pro 10.5.
Also: as I did the testing, I happened to notice that the section links in the Safari mobile view navigated to a seemingly random place within the article if the page had already been loaded and one or more preceding sections had previously been opened. In the preceding case, trying the "Australia" links immediately after the "sight vocabulary" links caused this behavior (e.g., by clicking on one of the "sight vocabulary" links, then clicking the "back" button twice [once to return to the top of the page and once to go back to the sandbox] and then immediately clicking on one of the Australia links). I'm wondering if may be because the section's physical location is being calculated assuming that all sections are collapsed. Once I collapsed all above sections and tried again, the section link sent me to the correct place.