Product doesn't seem to hide variants. It only provides the option to permanently delete them.
Thanks for your review - you are correct, there is no way in Shopify to hide a variant, variants simply do not have a toggle to show or hide them in the Shopify platform.
We do however offer an alternative work around, in that it can delete all but the last variant when they sell out.
You can then use the Hide Sold Out feature to hide the product.