Open-Source does mean that I (as an individual) have a lot of rights, including having the right to fork it in case I don't like the current stewardship.
Most of the Android eco-system is actually as
closed as with every other platform
That's bullshit.The Android eco-system includes thousands of open-sourced Java libraries and cross-platform development tools that are also open-source. I can develop Android apps on Linux or Windows or OS X, depending on my mood. And I can modify those tools to make me more productive.
Yes, I don't have a direct influence on what Samsung might deploy on their phones, or on the code getting deployed in Android's master ; but then again, it's equally hard to have that effect on Linux, the kernel.
If you don't like it, fork it. That's what open source is about.
except the false advertising
An open-source license is a legally binding contract. That's not word of mouth or advertising.