What is the deal with the new weird Gazelle chain case design?
Found an English Language site that explains it. From 

http://www.cycle-heaven.co.uk/bikes/brands/gazelle/gazelle-chamonix-c7-women-s-2015/


  All Chamonixs feature Gazelle's innovative transmission design with a
  chain tensioner inside the chain case. This keeps the chain always at
  the correct tension, needing less maintenance and giving a quieter
  ride. The frame is able to use vertical rear droputs which makes wheel
  removal and puncture repairs much easier.  We also think it gives the
  bike a more streamlined look.


It's called the FlowLine chaincase - here's a picture of it:



So it's not what you think. I can't say whether it's a good idea or not, but it seems at least a plausible solution for a City Bike.