I'd argue that that is the wrong question, motive doesn't come into play in this law (specifically: The merger doctrine). You should rather be asking the hypothetical version. If someone tried to make a second system that could run the software, would they have had to copy the API? If so the API is not copyrightable.

The existence of those works that run on both means you really need to start coughing up evidence for your repeated assertion that Google's motives were strictly about something else.