Hisham, I think they just get two Tamiya kits and put them in a room together for a few days... and then you get this little one.
Seriously though, it must of course be much easier and quicker simply to measure up another maker's kit and then produce your own CAD drawings from it, rather than having to go out and crawl over the real thing yourself. Especially when scaling down, I guess any errors in your measurements become less. And I imagine that since it follows the real thing just as much as the original kit does, so long as you haven't used any mechanical means to copy it, then it would be hard to bring about any copyright infringement, wouldn't it?
Of course, I have no doubt that this is not what happened in this case.