Hi norlin,
Sorry for not responding sooner to your post. I looked into the issue that you described, and I believe everything here is actually working correctly. If you add a component to a class with the EditDefaultsOnly specifier, then create a Blueprint of the class and modify the component’s values, those changes will persist in the Blueprint even if you later remove the EditDefaultsOnly specifier. If you want the component’s values to reset to the default values after removing the EditDefaultsOnly specifier, you would need to create a new Blueprint.
I am somewhat unsure about what you were seeing in the “update” section of your post. I added the EditDefaultsOnly specifier back into the parent class, and then changed the Location of the component again and the component would then use the new Location that I had set (this was in 4.18.3, so it may have been an issue that has been fixed since you noticed it).