Why the web-based routing and the map-mathing code routing generate different route?

There is a gate, the web-based generates a normal route, but the map-mathing code generates a route with roundabout. How can I avoid this? Thank you for your help!
https://graphhopper.com/maps/?point=31.030776%2C121.420727&point=31.02828%2C121.421676&locale=zh-CN&elevation=true&profile=car&use_miles=false&selected_detail=Elevation&layer=OpenStreetMap

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