harg
The mapping seems to be correct and corresponds to what Bing shows in satellite view. OSM doesn't map any turn restrictions at that junction and https://www.openstreetmap.org/directions?engine=graphhopper_car&route=51.49913%2C-0.10469%3B51.49877%2C-0.10420 shows that it's possible to plan a route turning left from Blackfriars to Borough Road. Yes, it goes via one small segment of the roundabout, but that's completely correct too. If there's traffic on the roundabout into Borough Road, traffic from Blackfriars should give way to it before turning. So the roundabout can't really be ignored -- it's there, and there doesn't appear to be a marked left turn bypass, so we should continue to map it.