When you generate a sample XML file from a schema, not all the elements and attributes are created in the XML file.
All required elements and attributes should be created, but optional items will only be created up to a given depth, after optional items are randomly added, so there is no guarantee they will appear.
As a choice can only have one of the options within it, the choice of which to use in the XML is made randomly. So some options may appear to be ignored.
Turn up the values for the following values within the sample generation wizard:
"Force the creation of optional entities to a depth of"
"Stop Creating optional items after a depth of"
See the help for the XML Sample Builder Wizard
for more information about these values.