Duplicate results for predicate queries

[hannahbast]

The following query (all cities, restricted to Shanghai) gives two identical rows. Shouldn't it be only one row? Confusingly, on https://query.wikidata.org the query gives four identical rows.

PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
SELECT ?x WHERE {
  VALUES ?x { wd:Q8686 }
  ?x wdt:P31/wdt:P279* wd:Q515 . 
}

[hannahbast]

The result is correct: There are two paths leading to wd:Q515. One via wd:Q1066538 ("National Central City") and one via wdt:P31 without using wdt:P279. The wdt:P279* alone should produce no duplicates (and there is no evidence that it does).

So all fine, just confusing.