My MK11C also appears to work in "ambient/full" mode. Both levels change when the reverb control is increased i.e. at its minimum setting you can switch between no reverb and moderate reverb. As you increase the reverb level, the amount of reverb in both modes increases, but maintains a distinct difference until you get towards the maximum reverb level.
Could be a dirty contact in mine as it was unused for years before I got it, but I have a feeling that this is how it was designed to work, regardless of what is in the manual for the MK11.
