old question about the quality of Wikidata. Yet again the same questions are raised. Yet again the same answers are given. The same questions are raised but with a "different" angle; "our policies have it that"... It is really old wine in new caskets.
Wikidata is immature, it does not include enough data. This is also true for Wikipedia as well; both do not include the sum of all knowledge. Arguably, Wikidata is more inclusive.
Several Wikipedias have a policy requiring sources for facts. What Wikidata does is compare its data with other sources and flag differences. This process is immature but it exists. It is probably as reliable or better than the Wikipedia way of relying on one source at a time.
When someone enters incorrect data at three sources, he will be asked not to do it again or else... Just like in any Wikipedia.
As Wikidata matures, such questions will be increasingly desperate because who will care in the end?