Pinning feels half-functional. It does pin notes, but the pin doesn’t seem to really mean anything if selecting a link or note file doesn’t open the pinned tab of that note.
Create 2 notes, NoteA and NoteB. Now pin NoteA. In NoteB create a link to NoteA and click it. Note how NoteB’s tab navigates to NateA instead of just opening the pinned NoteA tab. Repeat this by using the file hierarchy view, it does the same thing.
When selecting a note via link or file, it first attempts to open any pinned tab of that note before opening or navigating the current tab to that note.
Personally I always saw it as a “lock in place” functionality. You can use the pin to lock notes in place as custom UI.
For example, I have a pinned note in my sidebar, that always displays a query of my last 20 days of recent notes. It is pinned in reading mode, so I can click on the links. But if I ever want to edit it, I want it to open in the main tab area, and not change in the sidebar, and certainly not move my keyboard focus to the sidebar.
But perhaps “locked” would be a less ambiguous term.
When I follow a link to a note that’s open in a non-pinned tab, Obsidian takes me to the tab. So it surprises me when I follow a link to a note that’s open in a pinned tab and Obsidian doesn’t take me there. The behavior is inconsistent.
An exception for @rigmarole’s sidebar case would make sense to me. I don’t expect the same behavior of sidebar notes.