Hi @Steph, thank you for sharing your experience.
I have been using the "truly portable" version described in Tentative procedure to make Joplin Portable truly portable on Windows for several months, and it works perfectly. Moreover, I no longer have to wait the long startup time required by the "official" Portable version, which extracts the entire app every time before running.
You might want to try it!
I cannot see the post you quoted (I believe because it has been deleted).
I hope there wasn't anything dangerous in the suggested BAT file.
However, let me clarify that the procedure mentioned above does not require any BAT script (nor any other script); it just needs a simple shortcut.
Let me know if you need any clarification on that