Where does it say that? I've seen a lot of posts claiming just the opposite.
You can't just take a setup designed for type-A ports and mechanically convert them to type-C, because that would allow you to make an A-to-A connection. But that's not a blocker for a properly-designed hub.
I bet this is fully artificial limitation sneaked into the spec by people not wanting "stuff working without PCs"
It has one USB Type-C in with 3 USB Type-C out plus 4 USB Standard-A out. One of the C outputs supports downstream charging. Should just be a matter of time until hubs using this chip are widely available.
Every "hub" I've seen has maaaybe twl USB-C ports and two or three USB-A ports—which makes me think that USB-A will never die and we'll be stuck with both of them forever.