HI JLD ,
Thank you very much for your post.
Please, understand that ATUM has nothing to do with shopping limitation. Its all WooCommerce.
To hide in stock or to change how that appear - please, go to woocommerce settings
Enabling ATUM inventory control only shows products in Stock Central - it does not have any effect on how people order.
There is a full ATUM documentation on this forum, please, do have a look to find out what each function does.
Hope this helps.