Correct me if I am wrong, but to label a block chord, you look at the chord in the bass, then you look at the note or notes in the melody that line up exactly vertically with that chord in the bass, and you try and identify the chord.
But what if we have a broken chord instead? Does this vertical analysis still hold up, or are you supposed to look at the broken chord as one whole (a block chord) rather than separate notes with a corresponding melody note (separate 2 note "chords" in their own right)? If it is as one whole block chord, how do you know which melody note was intended to "line up" with that chord? I suppose it's not possible to know, so you simply label the broken chord without considering the melody? Or take your best guess?