Arctaurus, well as usual if in doubt follow the safest course of action, which in this case is adding 40 ft. However, if you check the design criteria for DA creation it includes corrections for the temperatures, but I couldn't find out down to which T is it good. I haven't experienced corrections for DA, with OAT UP to -30 C, flying in the northern USA. Maybe we were doing wrong, I am not sure. Logically, I agree with you it would makes sense, I am wondering why airbus didn't include it?
Cheers.