KfW 55 with 36.5 cm aerated concrete (λ 0.07 W/mK) should no longer be possible under the 2016 Energy Saving Ordinance. The proof should be provided by the supplier before the contract conclusion (complete thermal protection proof by an expert in sound and thermal protection, e.g. a structural engineer including calculations according to the Renewable Energy Heat Act) or guaranteed. Likewise, the sound insulation of the exterior walls is an issue: depending on the noise level at the construction site, the aerated concrete exterior wall is not / not readily able to ensure sufficient minimum sound insulation according to DIN 4109. This should also be proven by the supplier.
I agree with sentences 2-4, but I cannot understand sentence 1. First of all, nothing has changed regarding KFW55 due to the turn of the year; KFW55 remains KFW55 and has always referred to the reference building. Secondly, for example, the required U-value for KFW55 according to reference values (possible from 01.04.2016) is 0.20 for the exterior wall. With lambda 0.07 and 36.5 cm, you achieve about 0.18 to 0.19. So it is not a problem.
Regarding the first post: A subsidized KFW efficiency house could also mean KFW70 until 01.04.2016, as this program still existed until then. KFW-eligible can also, as already mentioned by Rübe1, simply mean that it can be subsidized through the KfW home ownership program and has nothing to do with the KFW efficiency house.
Because aside from the fact that KFW55 is easily possible with 36.5 cm walls: The blocks are significantly more expensive than normal blocks with lambda 0.09, and therefore I almost doubt that these are really included in the standard offer.