This business of CA is all a bit odd. As Doug says, it really does matter even if you are working in B/W, because it smudges the edges of things like tree branches against the sky. When I was working with film on the 'Blad, I never really saw any CA at all, even when shooting colour. Then, when I got the 39MP back, to my horror I had loads of CA with the 50mm and to a lesser extent the 60mm. Really bad, in certain circumstances. The 80mm and upwards were fine. I just thought that this was inevitable with old W/A lenses and digital sensors, and resigned myself to dealing with it in software.
Then, I discovered I had a defect on my brand-new CFV back, a vertical magenta line which showed up at 100% about one third in from the left of the frame (a "column fault", they called it). To cut a very long story short, the DB went back to Denmark under warranty, they tried to fix it by re-calibrating but could not, and in the end they fitted a brand-new Kodak sensor, checked it through and returned it.
All was good, and then I realised after a few weeks of use that the CA problem with my W/A lenses had gone. Well, just a tiny bit of fringing if you went mad with TV aerials against the light, but nothing like what it had been. In fact I now have to really look for CA to find it at all. Now, I don't understand the tech stuff behind all of this, but it seems to me that CA is not necessarily just a lens problem, but can also be affected by sensor alignment and calibration too, somehow. Which might explain why we are getting conflicting reports on this with regard to the Leica S2.
Edit - having just re-read the above, I am struck by the thought that it all sounds pretty improbable, because how could the sensor calibration affect CA? And yet, that's what seemed to happen.