Quote - In case any of you understand Python, I'm just doing os.path.join(vssFolder, 'macro1.py') 

That is the official way to join folder names with file names.

Why is that not producing the desired outcome?

If you inspect "poserStartup.py" (location runtime/python/poserscripts), you may find the reason.
"Buttons" aren't started with Pythons function exec anymore. They are started via Posers build-in "ExecFile". This function accepts only ":" as path-delimeter.

Insteed of writing os.path.join( ... ), write:

path=":".join(("path 1", "path 2", "path 3"))

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