There are 3 points which I make in that tutorial, and I will enumerate them.
Blogger / Google makes it easy for us to (inadvertently) create extra Blogger accounts.
When we login to Blogger, we login to a Blogger account - not to a blog.
When we login to Blogger, we can be affected by a Google login cookie.
Those 3 points, considered together, will explain why you observe that Google police merge and combine two blogs. I'm going to suggest that you follow me, as you are not the first person who has had this experience. These are 3 different articles - each of which relates to one point, above.