Consider the following examples: 1. Plasma/FAQ#How does Plasma work? links to the English page.
Special:MyLanguage/Plasma/FAQ#How does Plasma work? in any locale you will also be linked to the English page (broken localized links).
2. Plasma/FAQ/4.4/Configuration is valid page that can be linked, e.g. Plasma/FAQ/4.4/Configuration#Can_I_move_the_applets_on_the_panel.3F
On the other hand
Plasma/FAQ/Configuration#Can_I_move_the_applets_on_the_panel.3F points to nowhere (broken subpages).
Plasma/FAQ has only one purpose - to direct anyone searching to the latest version. It doesn't have any content, any sections, any subpages, so I'm surprised that even your first example works. I wouldn't have expected any links to be formulated against Plasma/FAQ at all - but against the versioned links (after all, the reader doesn't actually see that part of the link anyway). Now at last I understand where we started from :-) Yes, you are correct, I made a mistake there. Sorry about that, but I really did need to understand what you were pointing out.