Hi,
I am running tests to test various level meters that still do RMS like the internal one in Wavelab, and I used the test generator found in the Steinberg plugins folder, and I was surprised with a 100 Hz sine wave at the very visible harmonics shown on the spectrometer ! Ok,this is not the most useful plugin in the world, but at least when you need one, it should be clean in an app like Wavelab ! 
Best regards
Mark
I don’t see anything wrong, with a quick test. Any screenshot to show?