You'd be surprised at how fast mild steel can rust up when neglected and left in the elements, but maybe you guys do have a point. Perhaps the color of rust is too dark, in which case a lighter orange colored rust would be more appropriate in this case. It really depends on how long it was neglected and to what elements it was exposed, which in this case would most likely be a lot of moisture via rain or perhaps snow.
Either way it is a striking vehicle colored and weathered the way it is, even if it is perhaps a tad impractical I would very much enjoy seeing it on my shelf.