The description for this attribute does not say if it refers to content or content and metadata.
The definition for cmis:folder would imply it is both.

Section 2.1.9.2.1 suggests secondary types SHOULD be fullTextIndexed FALSE.
The secondary types in 2.1.16 all have this as <repository-specific>

It should be clear that the meaning of this flag is repository specific but would be expected to include both content and metadata.
All values should be <repository-specific>