It's actually pretty factual. They open sourced Darwin/WebKit/LLVM/Clang, and legitimized BSD and Unix as a consumer product via OS X... in 2001/2005/2005. The only "big" company that I can think of that made a move that big was Mozilla, which arguably doesn't even compare to a company as huge as Apple. Plus Mozilla open sourced itself out of pure desparation from pressure via Internet Explorer (which, I might remind you, was one of the worst proprietary pieces of shit to scorch this earth, by none other than Microsoft).
It's only been a recent thing where companies like Google/Microsoft have been embracing open source. Companies like Gitlab/Docker weren't even concievable back then.