Remember that international standards bodies approve open standards, but for some reasons they seem to copyright their documentation, like ISO standards. There is a lot of pressure for open standards documentation to also be fully open and available.
No, isn’t USB 4 (USB-C) an open standard which is why it is cheaper to produce than Thunderbolt and others? See https://www.digitaltrends.com/computing/usb-4-everything-you-need-to-know/.
Remember that international standards bodies approve open standards, but for some reasons they seem to copyright their documentation, like ISO standards. There is a lot of pressure for open standards documentation to also be fully open and available.
So is it open hardware or not?
USB-C and USB 4 different, USB-C is the physical connector while USB 4 is the protocol used to exchange information.
USB 4 is half proprietary half open (the licensing is very hard to understand on purpose) but i can’t find much on USB-C licensing