Oh that's interesting. That might be an extra reason why devices are still preferentially coming with USB3 type A plugs on the other end - it's actually more flexible that way? I am in fact plugging both of my new USB-C devices into a USB3 hub, and had no idea I wouldn't have been able to do the same with USB-C cables and hub.
(I assume you can still have a USB3 hub with type A sockets on it, plugged in to a USB-C port? - edit: oh, just noticed a sibling comment says this doesn't seem to exist either. Now that is very odd.)
Usb 3 hubs with a USB-C upstream certainly exist, all the docks out there are functionally that, and there are also dedicated hubs as well.
Here’s the one i use:
Anker USB C Hub, Aluminum USB C Adapter with 4 USB 3.0 Ports, for MacBook Pro 2018/2017, ChromeBook, XPS, Galaxy S9/S8, and More https://www.amazon.com/dp/B07DFYQXY7
(I assume you can still have a USB3 hub with type A sockets on it, plugged in to a USB-C port? - edit: oh, just noticed a sibling comment says this doesn't seem to exist either. Now that is very odd.)