By "aerodynamic data" Airbus means AoA.
Using FMGC computed weight instead of AoA means that the data is consistent between both sides of the flight deck and more accurate as well - I'm sure someone told me that the GW can only be estimated to within about 3 tonnes from AoA data, but is probably within a couple of hundred kilograms from the loadsheet.
Second point - dunno. There are some failure conditions that ask for the aircraft to be landed at VLS (which is acceptable anyway) and perhaps there's an issue with control authority given the size and relative positions of the bigger engines. Just a guess though.