Basically every wikipedia page (across languages) is linked to wikidata, and some infoboxes are generated directly from wikidata, so they're seperate, but overlapping and increasingly so.
I agree there is strong overlap between entities, and also infobox values, but both wikidata and wikipedia has many more disjoint datapoints: many tables, factual statements in wikipedia which are not in wikidata, and many statements in wikidata which are not in wikipedia.