Earlier quoted context omitted.
I guess that's the joke. Nobody cares about phone rotational inertia, the fact that someone would measure it is funny as is.
People actually care, this got investigated because early reviewers “felt” the phone was much lighter than it actually is (which is quite welcome). The lower moment of inertia is the cause of that difference.
I refuse to believe anybody at all cares about how light or heavy their phone weighs or how light it "feels".