Hey, great bug report with a solid root cause analysis.
This is a confirmed bug. UnifiedSidebarPart really doesn’t track focus and doesn’t set sideBarFocus. The related issue with focusActiveEditorGroup was already reported here: workbench.action.focusActiveEditorGroup does not move focus from sidebar when triggered via keybinding, and the root cause is the same.
The team is aware. There’s no timeline yet, but your report and code analysis help prioritize the fix.
The workaround you found !editorFocus && !terminalFocus && !panelFocus is the best option for now. Let me know if you find something better.