This is correct - there are 6 Windows 10 SKUs[1]. 4 if you exclude the mobile SKUs. The "only 2 SKUs" was just a rumour/wish.
I'm echoing speculation I read elsewhere: the reason for the numerous versions is Federal Money. The US government demands that it pays the lowest price the vendors offers an item for. Since Microsoft likes to offer discounts to universities, the government would be entitled to the lowest discounted price on the SKU. Their solution is to make Education & Enterprise versions and maintain the price disparity. Money trumps simplicity.
I'm echoing speculation I read elsewhere: the reason for the numerous versions is Federal Money. The US government demands that it pays the lowest price the vendors offers an item for. Since Microsoft likes to offer discounts to universities, the government would be entitled to the lowest discounted price on the SKU. Their solution is to make Education & Enterprise versions and maintain the price disparity. Money trumps simplicity.
https://blogs.windows.com/bloggingwindows/2015/05/13/introdu...
(edited for clarity)