That is an excellent and easy to understand explanation of Android security from the user perspective, and is as valid today as it was a few years ago.
The only thing that I would add to it today is relative to what I've already discussed in my post about "root" above. More specifically, if you read through the full list of permissions detailed in that article, keep in mind that when root privilege is granted to any app, it effectively opens all of those other permissions at once, and adds more, such as permission for full OS access, to both read, modify and add to operating system software or data, etc. Such changes to the system cannot be fixed or purged by a Factory data reset.
I looked at the "thanks" on that post, and am impressed (but not surpized) at how popular it has been. This seems like a very good place to reference it. Thank you.