Hmmm... I rewatched it, and a few buildings had extra detail; but were not up to the usual level of detail I see in Sketchup buildings in my area. The ones with the round stacks on top are the specific ones that you couldn't make in Map Maker without breaking the rules. Almost all of them, though, could be produced in Map Maker. You can get as complicated as you want with the foundation and then add height to get buildings with relief on the sides. For buildings that connect to others with dramatically different roof heights, the guidelines permit those to be drawn as two separate buildings with two heights.
Since it is London, I wouldn't doubt that they were all done in Sketchup; two years early my area was all done in Sketchup when we hosted the Olympics. Some smaller items, such as washroom buildings and statues, were created as simple cubes. This is actually very annoying; when some were torn down during later construction I could not delete them, even through they were something that could have been made just be adding height to a polygon. Report a Problem took months to get them removed.