There are many, many ways to transfer files. Many phones present themselves as a Mass Storage device (i.e. same as a thumb drive). Others use the Media Transfer Protocol. In any case, your device end has to be configured as such, which cannot be done from a Windows host. USB on the Go (and by extension, USB-C) offers some very limited abilities for something to switch between host and device (master/slave), but it’s up to each device to enable that functionality.

When most of us share files on a PC, we are using SMB. This is what Windows typically means by sharing files, and is network-based.

Regardless, you always have to configure each side on what/how to share, and how to access that share. Most phones have a default configuration for this (and it’s not everything on your phone), and Windows makes this type of access easy and direct. Again, there are other options, such as the Android Debug Bridge, which are much more complicated.

(As for the identifying chip, there are chips that present themselves in different ways on demand. It is a massive security risk, and has been exploited in the past. Examples are fake keyboards, fake network adapters, and even fake storage - although that’s usually technically real, and used to deliver a malicious payload)