You are 100% correct. Open source has a common definition the vast majority of the world uses, a company can proclaim their own definition, but it doesn't magically change the language. Nobody is thinking about, or even aware of, the OSI, when using the term. The correct term people should be using is "OSI approved", or something similar, although that's no more meaningful or useful as a "bob approved" license, where bob is some random nobody.