I think the reason they give you the opportunity to download another file is simply so that the gcode can be tweeked (for variable such as layer height, hotend

I think the reason they give you the opportunity to download another file is simply so that the gcode can be tweeked (for variable such as layer height, hotend temp, max acceleration of head etc.). It could be, for instance, that with your particular filament the gcode doesn't tell the hot end to get hot enough, and you end up with layers splitting. Or worse, a huge tangle of melted filament.