I have just discovered the new button to delete/remove properties from a product. Here is how it works:
While editing the product, there is an option to view ‘PRODUCT PROPERTIES’ This then shows any properties that have been assigned to the product. To delete a property you can click on the bin icon to the right of the product - see screen shot below.
Clicking the ‘x’ beside the property name does not result in a permanent removal of the property.