Let me make an amendment to my original comment- my old and completely empty product types are in fact disappearing after I make sure that no products are affiliated with that specific product type. It didn't happen instantaneously which is what caused me to write on here a few days ago, but I believe they started to disappear maybe about an hour after I emptied that type. I have been going to all products, more filters, product type, selecting the one that I want to delete (which shows all items with the selected product type) then either deleting the products if applicable or changing to a newer, more appropriate product type, until none show up under that filter. About an hour later, the old product type disappears from the list when creating a new product or from the list when filtering. I hope this info helps!
We are trying to clean up our product types as well, and would LOVE to delete old Product Types as there is way too much room for error with similar existing ones - when training new employees etc this is very risky as so much relys on porduct types (ie auto filling collections, merchandising, SEO etc) = Loss in sales. SHOPIFY YOU NEED TO FIX THIS!!!!