I may be misreading the link, but proprietary seems to be using to describe non-open source binary blobs. This is typical of drivers, most chips on cellphones

I may be misreading the link, but proprietary seems to be using to describe non-open source binary blobs. This is typical of drivers, most chips on cellphones do not have open source software to control them. Typically these pieces of software are modem/radio chips etc.