Do contrib modules have to be set to expose settings variables to Strongarm? I'd like to push everything into Features for the sake of versioning and migration of my site configuration.

Does a contrib module have to be purposefully set up to expose its configuration variables to Strongarm?
Looking at strongarm_vars_load I can see that it loads all variables in the variables table using ctools_export_load_object regardless of any special consideration (other than variables already controlled via strongarm in features). 

When I've used it in the past I've never had to specifically define the variables for strongarm to use.