"Production-grade hardware design files... Study real CAD... Learn from how real products are built... STEP"

I'm sorry, I hate to be that guy, but while STEP files are often used as the final export to the contract manufacturer to cut the molds, or for some level of fit checking, they're not used for anything else. The real engineering that you can actually learn from is in the SolidWorks (or equivalent) part files, and you'll note that they're not offering those.