I did a file - "Save As" and re-saved the script as a .sb8 file and the resulting build now passes the target OS test. It had been saved originally as a .sb6 file and just re-saved anytime changes were made.

I'm not sure why just saving "as" with the new extension would resolve the issue, but it appears that it did.

Thank you for you help and patience with this issue. We've used SetupBuilder for years and it has always provided the features and support we've needed.