Hi, 

the idea was to map the sidewalks only where they are somewhat separated from the road, e.g. by parking spots and trees, and thus sometimes have a different shape than the road. Additionally other segments of the same road for consistency, where the separation is just the curb (which is also a relevant separation for wheelchairs).

I see the problem with the routing, though, and would like to find a solution to it. It seems like the problem in your exemplary route could be solved by connecting the sidewalks with the road at the T-shaped crossings (e.g. crossing:unmarked). Note that the Alte Vaalser Straße does (and did) not have sidewalk=both.