Why are there harmonics created by the TestGenerator?

The sine wave in the TestGenerator isn’t clean. There are multiple harmonics generated by a simple sine wave.
This doesn’t happen with the ToneGenerator in Presonus Studio One or MeldaProduction’s Oscillator fro example (see right half of the screenshot).
So for “testing” purposes this is (depending on the test) more or less unusable because the signal isn’t clean. This might be good for analog sounding synths (Halion, Retrologue, …) but for a “TestGenerator” this is a bit sloppy.
Any thoughts from the professionals?
TestGenerator Harmonics.jpg

See https://www.steinberg.net/forums/viewtopic.php?f=231&t=99710

Thanks. Didn’t do my “search” homework then.
Hopefully this is going to be fixed in the future as the TestGenerator is very handy tool.