If you're interested in reading a bit more about the effect you've stumbled upon, there's information here. https://www.ntnu.edu/documents/1001201110/1266017954/DAFx-15_submission_5.pdf/09f59775-5d01-4699-99ee-995b23dedea4
Sorry I didn't notice this thread the first time it popped up. The Ring Modulator does indeed quantize to half steps when you turn tempo mode on. The display still shows the value in Hz, but you'll notice that the step size changes, and as you sweep it you should hear that it's jumping by half steps. For instance you can pull it directly to 440, and that will be an A.