thanks for the request.
In general this is really hard to solve. GraphHopper currently does not support turn lanes. There is a PR for this. Which could in the future help with generating turn instructions.
Currently, GraphHopper calculates turn instructions mostly by looking at the geometries of the route and a small set of tags.
BTW here are both situations in Mapilary, 1 and 2.
I think navigation should be still possible, since the left turn, could be still considered as a continue without the signs and arrows on the pavement. However, a left-turn would be better suited.