> The company “undermines” the ability of iPhone users to message with owners of other types of smartphones, like those running the Android operating system, the government said. That divide — epitomized by the green bubbles that show an Android owner’s messages — sent a signal that other smartphones were lower quality than the iPhone, according to the lawsuit.
I read that as 'interop' is a secondary issue, if an issue at all; the actual case is the green/blue segregation. If Apple embedded a fingerprint in every interoperable message and shown blue messages for iMessage-sent content, green background for others, it'd still be a problem even if messages are otherwise identical - unless all the features truly work on both, in which case the color split is purely status signaling.