Sorry for the huge delay in replying. I stumbled on this question by accident and since I happen to know the answer, I thought I’d tell you.
IsElevated() returns true if the content is prioritized for display in the menu when you are creating a new content. The menu only displays 5 items, so the plug-in developer can elevate the most important ones so that they appear in the top 5.
IsBuiltIn() returns true only for contents that are built-in to the RDK. This is how the RDK can tell if it owns the code for the content or if a 3rd party does.