When I enable a feature that includes just DS default settings without any variables or anything, those default settings are not applied.
Features puts the default settings in a custom MODULE.features.ds.inc file which is also not included during rebuild unless specifically specified.
To me it looks like ds_default_settings support in features is completely broken because of this making this very critical, but the lack of issues here (maybe because its just for D6?) makes me curious if its just me.
The attached patch fixes my use case but I have not tried to think through more scenarios / use-cases.