The wiki says 
"An area (closed way or multipolygon) tagged with highway=pedestrian + area=yes". 

According to my understanding, that means that multipolygons should also be tagged with area=yes. So you would say that that this is wrong?

Would you say it is a false positive that OSMI claims that the escalators to AtmosFear are unconnected nodes in terms of routing? Or how would one fix that?