Earlier quoted context omitted.
Question from a layman: Does "interoperability" as a concept have any legal relevance here? Like focusing on programmer skills seems kind of beside the point, which is really for two pieces of software to be able to interoperate.
Yes, interoperability is relevant, because it affects the necessity of copying that particular code rather than making one's own substitute, which in turn affects fair use. But Google's lawyers (inexplicably, in my opinion) failed to talk much about the fact that many Java libraries are interoperable between Android and Oracle Java, leaving the courts to think only in terms of full applications which are not interope…
To argue interoperability Google would have needed to copy the entire JAVA SE API.
The key difference is that Java SE (designed for desktops) API was considered by Google mostly not required on smartphone/mobile devices envisaged for Android. Sun would only licence Java SE complete (Sun was the one wanting complete interoperability).
To the extent the concept of interoperability enters into it, it was on the human side; the arguments were about leveraging existing programmer knowledge to the extent that Android's requirements were shared with and common to Java SE.