FYI, it's better to read it like this:
1 - Zion
2 - Culver, Barrett
3 - Morant, Clarke, Porter
4 -Hayes, Horton-Tucker, White, Hunter, Bitadze, Reddish, Williams, Langford, Garland, Washington, Porter, Bol, Jones, Alexander-Walker
The Sepien puts them in the tiers to avoid generic listing for listing purposes. And they were the highest on Porter last year, so I'm assuming they're assuming he's healthy in his career.