Hello - this is incorrect. If you put a single unique tag on a single product as a test, you know exactly where all instances of it are because you only added it one time to one product, and delete it - it still exists.  

This answer does not address the fact that you are giving instructions on how to delete tags off of multiple products, transfers, customers, blog posts, orders, or draft orders, which is not the question.  The question is - how to fully delete a tag ...