I imagine what happened is that they designed it with flat plates so that it could press whole vegetables. However this didn't work, because as you need to mill

I imagine what happened is that they designed it with flat plates so that it could press whole vegetables. However this didn't work, because as you need to mill anything except soft fruit before they are pressed. They changed the composition of the produce packs so that it did work. However by doing this they'd made the packs so easy to press that a roller (or your bare hands) were sufficient. By this point they'd already designed this beautiful over-engineered solution with flat plates, so probably didn't even try using rollers at that point.