Not even Richard Stallman defines open source (or rather free software) like you do. [1] AOSP meets all of the criteria, and it's a code dump with a permissive license that you are free to fork and redistribute as you wish.
There's no rule that free software requires accepting pull requests from the entire world.
The beauty of open source is that Stallman doesnt really matter. There is no community developing around Android except for the google play store because to do so would be futile. (Yes I actually READ the article).
If a text blob of nonsense at the top of a source file makes you open source then WOW. How about Doge-Source? Such open, very free.
There's no rule that free software requires accepting pull requests from the entire world.
[1] https://www.gnu.org/philosophy/free-sw.html