Just a correction. It's not openURL but NSWorkspace.shared.open that opens the document. It works fine, but, as I said, it's now bound to a file that is not where the user wants (the app is sandboxed, so it's hiding inside the container in the Library folder).

Logging sizes produces these numbers for heights of contentSize, viewSize, myContentSize on several iterations of run, quit, run: window content size 420.0, scroll content size 367.0, view size 305.5; window content size 420.0, scroll content size 367.0, view size 305.5; window content size 420.0, scroll content size 343.0, view size 305.5; window content size 420.0, scroll content size 367.0, view size 305.5 Why the variation?

This works, for future reference.