The top answer to this question (ADK and Eclipse woes - com.android.future and USBAccessory?) solved my issue (in a specific case), but I wondered why I needed to use the Google API and not the default Android API for implementing a IOIO board via USB. Why does this feature exist in the Google API 2.3.3 and not Android API 2.3.3 (since the android operating system is capable of supporting it... did the Android API developers just not add some additional functionality that makes the IOIO plugin tick?), and why is it not required to use the Google API for 4.2? Is this likely specific to the IOIO interface code I am using (https://github.com/ytai/ioio/wiki/Downloads#client-software-and-ioio-application-firmware-images)?
I would like to further understand the reason behind this so that I can better predict if I encounter a similar issue in the future with other libraries.
I do not have an idea about the USB issue you've mentioned. I just want to clarify why you need to use Google APIs instead of normal Android API in some cases.
Android code is open-source which means anyone can have access to it and can compile the code to make their own android enabled devices. Most of the device manufacturer choose Google's proprietary licensed version of Android which includes some of the Google services inbuilt which are closed source and are not included in the android source code.
These services include Google Play Store, Google Maps, Gmail, Admob etc. So if you want to use any of the Google services/features(which are not included in the usual Android features), you have to use Google APIs, which have support for these features.
An actual device running on Android OS may or may not support these features, depending upon the availability of Google Services in the installed ROM (These can be installed later if you have root access). For example Nokia X series won't support any Play Store, Google map or Google gaming services feature.
I suppose this is true in your case too.
PS: The above info is from my own experience and is not supported by any of the articles mentioned anywhere. Feel free to add references in the comments if you know any article supporting the facts.