Mostly unmodified is a kick ass term. Imma borrow that.
That's a standard term that Cars & Bids uses, they did the same when I sold a car on there a year ago. You have very little control of what you can put in the description. If your car gets accepted which seems random as I've tried to sell my pristine Touareg TDI on there and it kept getting declined despite them having some high mileage jalopies on there. Back on topic, once your car gets accepted you send them pictures and a description of the car and they create the listing with all of their wording such as "mostly unmodified", "some wear on driver seat", etc.
We'll be seeing more 'Reserve Not Met' on the site going forward as the car market is cooling. I have friends in the business and they are telling me that the market has cooled tremendously over just the last couple of weeks.