I originally posted this in the pit, but i don’t think i want to waste space in that thread. So I’m copying my post (which replies to sometime @Whack-a-Mole said there) to this thread, and deleting it there:
It’s up to the system to get it right. There are different paths to make that happen. USB-C is a complex system where the attached components all talk to each other and negotiate who will do what. It’s a marvel of modern computing, and usually works. Back when the USB standard was first introduced, the shape of the plug was part of the protocol to negotiate which component did what.
Could that USB-B jack be replaced with a USB-C jack today. Absolutely. But that would mean replacing a mechanically sturdy jack with an intrinsically fragile one, designed for situations where size matters. (Specifically, where small size is paramount.) That would be a downgrade on a device that can support a larger jack, and that’s often used in a way that leads to, for example, people tripping on the cable. Could it be replaced with a USB-A jack? No, not without violating the USB protocol, which no legitimate manufacturer wants to do.