@Vlad I finally determined the use-case that is causing me issues. You are corerct in that normal tab behavior mirrors Safari. It appears that when you close a tab, it returns to the tab that was active prior to the one you closed. However, the issue I'm experiencing is when I open a new tab from a pinned tab, then close that new tab, it does not return to the pinned tab despite it being the last tab I had active.
If you want, I can create a different issue that better describes this bug. I can also record it if needed. I have only tested this bug using the vertical sidebar as well, so I'm not sure if that is required.