It’s important to note that this is them moving in-development branches/features “behind closed doors”, not making Android closed source. Whenever a feature is ready they then merge it publicly. I know this community tends to be filled with purists, many of whom are well informed and reasoned, but I’m actually totally fine with this change. This kind of structure isn’t crazy uncommon, and I imagine it’s mainly an effort to stop tech journalists analysing random in-progress features for an article. Personally, I wouldn’t want to develop code with that kind of pressure.