If there are seats in the back it's not commercial.
A friend of mine has a Toureg .... has two seats in the front, none in the back and has the four doors - it is classed as a commercial vehicle.
My reading of your post is that the seats were put back in after the vehicle was certified as 'commercial'.
The vehicle you're looking at would not satisfy revenue for commercial status.
As an aside .... be happy with your expected miles per gallon .... both the friend I mentioned above and another person I know found that their Toureg diesels were guzzlers and they were easily putting €100 to €120 a week into them (prior to fuel price explosion).