There are not many great Mapillary images for this road, but this shows the current situation: https://www.mapillary.com/app/?pKey=108638188900202

In addition to what Wulf4096 wrote, cars at some crossroads are not allowed/able to cross the whole road either. See here https://osm.org/go/0HoHgI0Ey?layers=N&m= And yes, in case of one way for the Grindelallee road, this could technically be modeled with turn restrictions.

IMHO according to OSM "rules", there should be two ways here due to the barrier between the bus lines. However, some bus stops are in the middle of the road (s. the Mapillary link above), which would require separate bus-lane-ways around these stops to correctly model the layout of the lanes. Due to the different stop layouts (compare "Grindelhof" with "Universität/Staatsbibliothek" further south), this would probably result in quite a tangle of ways.

Even though it may not follow OSMs best-practices, modeling this road with three ways is IMHO a practical solution that doesn't cause any problems and is easy to maintain.