I would prefer paying a little more and not having the two stops where vendors were trying to sell us product. It would be much better to spend more time at the tour stops.
Our guide did a fairly good job describing the three sites. However, it would have been more meaningful if she also walked us around the Summer palace a little more. All we had was a 5 minute talk at the entrance.
All the small group tours have two shop steps and list in the itinerary. When you check the itinerary, you will find it, which is all for reducing your tour costs, and there is no forcing buying there, you can consider it as a rest. If you feel it uncomfortable, you can choose expensive private tours, even the more expensive no shopping steps private tour.