I beg to differ. Earlier in that description it says
Meet your guide and drive into the city for a half-day motor coach and walking tour,
Given that the excursion lasts a max 3.5 hours which includes free time (denoted by 'Shopping' at the top), the excursion shows you the sights of Vienna from the coach, plus a walking tour with free time to do your own thing. I took this tour, and thought it did an admirable job of exactly that. As we didn't want to shop, we had a pastry and coffee in a café. From the information given by the guide about the metro, we made our own way back to the centre later. There's a metro station close to the river morning.
There's not enough time in 3.5 hours to enter and tour Hofburg Palace, St. Stephan's cathedral, the Vienna State Opera concert hall and have time for shopping and a walking tour.
If you already know the city or prefer to visit certain places by all means skip this excursion. We didn't and enjoyed it.
mhb1757 had the bad luck to have a poor guide and get stuck in traffic. Luck of the draw, but our guide was good, explained a lot and gave a history, all of which was new to us.