Others have already addressed the technical issue you've run into with the referencing to sources that don't exist.
As to the style of citations, part of your confusion may come from WikiTree's own confusion about what method or style should be used. In short: Wiki mark-up, websites generally and WikiTree are not entirely compatible with WikiTree's preferred citation style.
While many social sciences use APA style citations and bibliographies, some use Chicago. Humanities subjects, including history — and by extension genealogy — favor Chicago (sometimes called Turabian). Chicago is what Elizabeth Shown Mills based Evidence Explained on, though she added her own variations and additional details to address the particular needs of citing specific records. There are strengths and weaknesses to EE, but it is the industry standard.
WikiTree's Alternative Sourcing Methods page says "There are many possibilities, some of which offer significant advantages over the methods described above and have been considered as replacements for the current recommendations. However, despite their advantages, these alternative methods are not recommended. And as with all style rules, if they are not recommended, they should not be used...[A]lternative methods that are not recommended [include]: Any citation style other than the Evidence Explained standards..." (emphasis added).
However, WikiTree:
- Has it's own "WikiTree Style" based somewhat on Chicago and EE. I don't have information about the source of the variations and off the top of my head can't tell you what all the variations are.
- Accepts any citation format, including things unique to individual users or websites, some of which may combine citations with extracts or abstracts, and partial citations (such as those written by FamilySearch, Ancestry and many users)
- Does not require inline citations of any format
Chicago (and therefore EE) requires inline citations and offers two methods. One is parenthetical, typically author-date, e.g. (Jones, 2011), combined with a full bibliographic reference list at the end. The other is footnotes combined with a full bibliographic reference list. Footnotes make it easier to reference page numbers for direct quotes or specific details, sources without authors, etc.
WikiTree uses neither of these methods. Inline footnotes only point to a bibliographic list. Separate citations are not made. This is not entirely unreasonable, given how short profiles are compared to a research paper or journal article.
However, it does mean that if you need to cite a specific place in the source, you need to use a non-Chicago method. If you write the citation to include, say, a page number, but the second use of the source references a different page number, you can write an entirely new citation to the same source just with a different page number (and then possibly a third citation to the same source with no page numbers, if it was also more broadly used). Or you can write a general bibliographic reference and find find a way to include the page number adjacent to the inline footnote number.
The use of span anchors to create a footnote citation (like the ones you've run across) that then points to a bibliographic list solves this issue very neatly. But they import with odd numbers from GEDCOMS and have a tendency to get mangled by members who aren't familiar with Wiki mark-up language, which is most of us. Using span anchors is very specifically "not recommended." If you come across them, you're encouraged to re-write the citations, which by default would be to a non-Chicago/EE style. Which is also not-recommended, but less not-recommended than span anchors.
