Back In Stock Variant Update
How to remove specific variants from the back in stock form
Go to the product in the admin of Shopify
Select the variant that needs to be removed from the Back In Stock form - scroll all the way down on the page until you see the metafield section.
There are two metafields that control this:
Sold out Forever
Hide BIS Form

Sold out forever metafield contols the add to cart button to say SOLD OUT
Hide BIS Form metafield controls the add to cart button to say OUT OF STOCK
All you have to do is select the metafield and select TRUE or FALSE. True, enables the button to change. False or blank = the button doesn't change to that option. Whichever is set to TRUE will be the option selected.
This works the same way on the WHOLESALE site too.