It is an easy way to visualise the quality of output they're capable of. Both in terms of how intricate and well styled their attempt is and how well the elements align with each other

It's a bit like comparing children’s drawings. There's how neat what they do is which is basically down to their fine motor skills, and then there is how complex and detailed what they do is. My 5 year old for instance isn't anything like as neat as my 9 year old. She just hasn't developed the fine control yet. But, she makes way more use of colour and puts effort into intricate details than the 9 year old does. He's happy to just draw basic shapes for things, but she includes as much detail as she can in things, eyes have an iris and pupil with eye lashes, clothes have stitching, buttons and pockets and so on

So with the models attempts at these you can see both the accuracy in terms of how well the different shapes line up (a lot of them have the rear wing floating away from the car) and then just how intricately they attempt to create the concept in the first place. The more capable models do seem to have more complicated concepts they try to recreate