That's the problem, the areas that SmartScreen ignores.If the samples are checked by the SmartScreen (they probably did not) the result will be close to 100%. SmartScreen Application Reputation has some limitations, for example, only BAT, CMD, JSE, VBE scripts can be checked and most malware scripts are VBS, JS, PS1. Also, executables downloaded by macros in Office documents are ignored by SmartScreen. There is also a problem with measuring properly the postinfection protection in the tests. So if one uses the above, without additional protection, Defender will score only an average (or below) detection rate.
But, the home users on Windows 10 can simply block Windows Script Host and set Constrained Language mode for PowerShell (2 simple reg tweaks) to get a decent protection against most new malware samples in the wild.