I've done a bit more testing with this. I've used both WinBatch 2016B and 2017B, both running on the same Windows 10 Professional system.
The test data is as follows:
I have a NTFS volume with a test directory "C:\Temp\Test01", and in that directory are 2 files, "Test.2018.txt" and "Test.txt".
If I call FileItemize() with the following parameter values of "C:\Temp\Test01\*" or "C:\Temp\Test01\*.*", I get results back that are identical in both cases, and both files are in the results.
If I call FileItemize() with "C:\Temp\Test01\Test*", I get back empty results.
If I call FileItemize() with "C:\Temp\Test01\Test*.*", I get back results that contain both files.
It's not clear to me whether there might be some factor in the O.S. version or configuration that may have any impact on this behavior.