This is an important point: HID class, as it was standardized, identifies each data item with a set of numbers called Usages, rather than with variable names.

The HID class spec has pre-defined over 1600 Usage IDs, organized into separate Usage Pages, for identifying each variable.  This is in fact how Windows keeps track (internally) of each data item.  These Usage numbers can tell a program what the data item is supposed to be used for.

THIS is how HID class makes it possible for the PC to talk to a wide variety of different devices without needed a custom device driver for each one.