* "APIs are not well-documented, and Google has changed them over time"

* "Carriers modify the OS to support their particular [...] idiosyncrasies."

* "Poor, inconsistent and conflicting documentation"

Not true. Google usually documents APIs well, and older versions of Android are forwards compatible to newer versions.

The SMS Api that the author used was a so-called "hidden API". These APIs are not documented on purpose, as they are not supposed to be used by developers. These are experimental APIs that can and mostly will change over time.

Hidden APIs are not part of the Android specification and they are not part of the Android compability test suite. Of course they do not work reliable on different versions of the operating system.

See: http://android-developers.blogspot.co.at/2013/10/getting-you...