The two go together. Why do you want to hide the fact?
Oh, and to answer your original question ... "What does the Free Shipping Radio button do?" ... it sets the product to be eligible for free shipping on the shipping page when shipping rates are calculated.
The other switch you just changed is intended to be used to display the Free Shipping icon on product page and all the product listings.
If you want to remove it from the main product listing for ALL products, you'll have to comment-out this line in the includes/modules/YOURTEMPLATE/product_listing.php file:
Code:
$lc_text .= '<br />' . (zen_get_show_product_switch($listing->fields['products_id'], 'ALWAYS_FREE_SHIPPING_IMAGE_SWITCH') ? (zen_get_product_is_always_free_shipping($listing->fields['products_id']) ? TEXT_PRODUCT_FREE_SHIPPING_ICON . '<br />' : '') : '');
You'll have to do similarly for all-products, new-products, featured, etc.