They talk about keeping the fraction of O2 constant, not the po2...

With the "constant" probably to be read as roughly constant or more favourable in its change than in most other SCR.

Looks very nice and I know the unit incorporates many innovative things. But remember that the pdf-document is probably just something intended for limited distribution. I would not draw too many conclusions about the actual workings of the various possible versions of the unit from it.