Is that correct? Is this because the kernel of macOS is BSD based so it's plugins fall into Unix OS?
Is my problem something else with importing data from tenable.io?
I don't think so, both Tenable.io and SecurityCenter should use the same plugins.
Why are we showing no vulnerable applications for macOS?
This filter does not show vulnerable applications for Mac OS, this filter shows operating systems running Mac OS X that are identified as no longer supported.