The abstract of that paper mentions the annihilation of the previously measure photons, where now, they aren't totally conserved, but not totally annihilated. Further down, they mention survival probability, and without access to the whole article, I can only conjecture, but I would go so far as to say that that is them implying that not ALL of their photons are conserved. Only 66% so far. They then mention tweaking that number.
Their measurement apparatus is basically a single atom in a superposed stated. It will require a fairly small amount of energy to shift it into a definite state. I'm thinking potentially orders below the photon energy that they launch at the aforementioned atom. If this is truly how they're doing their experiment, then they aren't truly leaving that photon EXACTLY the same. It does interact with the reflective surface. It does interact with the atom, and it does have the direction of it's momentum change if it's being reflected. All of these process do not happen with no energy transfer. It seems this team is merely exaggerating what they can do towards the head of the abstract, then throw in the limitations later.