But the article is saying you could have 10 Southern Baptist churches in one city with the same belief (not implausible in a large city) but they were each counted as a seperate church since Southern Baptist are independently operated. This, of course, drive the count up of Protestant denominations if you want to slice the cookie this way.
One would have to look at David A. Barretts World Christian Encyclopedia for a more detail understanding.
Southern Baptists should not be counted individually. They adhere to a common belief.
I will grant that not every non-denominational Cchurch, or every "Free" Baptist Churhc is unique. But in no way are they all the same either.
So they are not "one" and yet they are not "thousands" either. The point is that without an authority, there is nothing holding unity together. The Protestant principle leads naturally to division.