When you export a DataDynamic file (.ddf2 file) into a different file format, the only variables that cannot be exported are the multiples ones (multi-categorical and multi-dichotomous). The reason is basically that these are virtual variables, they don't exist in reality. Also the way we display them in DataDynamic is a chosen-one, but they can be displayed in other different ways.
So if the obtained file has less variables than the original one is because of the multiples, however the base variables are exported.