Instruments and hidden empty staves

In Hal Leonard's 'Billy Joel Keyboard Book', instruments that appear mid-way are in a rectangle at the top. Anything that plays from the start appears in the left, with no box.

In MuseScore 1.0, all instruments have bars at the beginning with their name (even if there's nothing until mid-way), and appear whenever it is being played.

Any opinions? Maybe you could have the option of the two.