Actually those techniques are failed because you've two different account, you may create same name but it will not display same profile URL.
When you create a new blog post in blogger it will show you which author is publishing a blog post.
If you go to your list of all blog post, then you will same thing, who is publisher of list of all blog post.
So there is no any setting right now avialable in blogger which help you to migrate your particular blog post to different author, but there is one way to do it.
- Backup your all blogger post, to do that go to setting >> other >> click on "backup content" button, and it will give you file name like blog-12-24-2017.xml
- Delete those blog post, which author name you want to delete/change.
- Import your all blog post from new author dashboard, to do that go to setting >> other >> and click on "import button" and unmark Automatically publish all imported posts and pages and then select the file name blog-12-24-2017.xml.
But one thing you should do first, collect your all blog post permalink, because it will change automatically once you import your same blog post again. Do you see the last "_24" in below permalink screenshot? which blogger add it automatically when you import blog post.
So first note down your all blog post permalink(URL) and when you done import, then change(same as old one) permalink of those blog post one by one, and then hit publish.