Denoise behaves differently past .5??

[poisenbery]

I was doing some experiments last night and found something very interesting.

With steps at 1, denoise seems to exhibit some behavior that I did not expect. At .49 denoise and 1 step, I could not see any visual differences in the image. But once denoise is raised past .5, the result is drastically different.

I was expecting the results to be visually similar since their denoise are so close, but this is not the case.

Does anyone have insight on why this happens, or if this is a bug? I wasn't able to test in Automatic1111 bc I don't use anymore.