[ihatehn]

On top of the OsmAnd user experience being a little rough (it can do a lot, but not gracefully) it relies on accurate OSM data underneath. So the best thing to do is at least make a Note on OSM, or edit it yourself, and mark that intersection as having a no-turns-allowed restriction.

Even Google is relying on user submissions to keep its stuff accurate these days, they just have money to pay editors and reviewers.