are you saying that you aren't allowed to adjust CAT 1 DH?
Hi, we do apply cold temp corrections to DA's and MDA's when OAT is 0 or below. But since this only involves setting it on the PFD rather than making any changes to the FMC it doesn't affect the validation of a VNAV approach (until -15C when we have to correct all the other alts as well).
That is my take on it anyway!