Hmm...in my test environment (PSTK 9.6, ONTAP 9.5P8) it actually appears that the cmdlet runs as expected, but the data returned is incorrect (both in the results output of the "New-NcSecurityTraceFilter" cmdlet as well as the "Get-NcSecurityTraceFilter" cmdlet) . Here's what it looked like when I tested it:
You can see it has a PS data type of "SecurityTraceFilterAttributes" (you can also see this in longer from in the source code of the function itself by de-compiling the DataONTAP.C.dll file inside of the PSTK module directory, but gettype() is quicker. )
Since it looks like it's a formatting bug, I checked out the "DataONTAP.C.Format.ps1xml" file in the module directory and searched for "SecurityTraceFilterAttributes" and found this:
Long story short, lines 10751 and 10754 are inverted - if you change 10751 to "WindowsName" and 10754 to "UnixName" and reload the module, it will fix the issue for your environment. Hopefully the PSTK developers are watching and can fix it in future versions of the module.