Hey raito,
Thank you for the message and the additional imagery input. A proper fix may be to add the tag barrier=bollard (barrier=bollard), on the middle of both of the ways I drew in, and to include turn restrictions. Adding these features should accurately represent the turn restrictions seen in mapillary.
Thanks,
M

Hey,
here is a current example of u_turn restrictions via ways working. osm.org/directions?engine=osrm_car&route=22.31154%2C114.16483%3B22.31160%2C114.16497#map=16/22.3152/114.1636 The extra segments are no longer needed. Thanks

Hey andrej], I apologize for any incorrect edits I may have made with old imagery. I noticed the roundabout has been touched by a couple other users since my edits so please feel free to make any correct changes with your local knowledge!