According to en:WP:V all material in articles needs to be verifiable. This often means the material has to be accompanied by inline references (en:WP:MINREF). This proposal neither includes a technical application to format inline references where they are needed nor addresses the significant problems of verifiability on Wikidata.
We can put aside the fact that Wikidata is notoriously bad in terms of references overall (Over half of statements on Wikidata do not have a source. Over half of "sourced" statements are sourced to Wikipedia, and according to the verifiability policy on the English Wikipedia, material on Wikipedia articles can't be sourced from other Wikipedia articles.) This is not relevant because the Reading team's proposal does not pull data from statements, but descriptions of items. Descriptions neither need or even support references on Wikidata. Descriptions do not even have to be summaries of statements (whether sourced or not). 100% of data pulled by this application will be unsourced.
A further complication is presented by the fact that Wikipedia has adopted the WMF Biographies of living people (BLP) resolution but Wikidata has not. Something like "American-born Greek", in the description of Maria Callas, would definitely be the kind of potentially contentious material that needs an inline citation to be displayed on Wikipedia, if the person was alive. Wikidata descriptions can consist of anything, but if this example is anywhere near typical, information pertaining to subjects' ethnicity is a BLP issue.
Wikidata simply isn't ready yet. Its standards and performance of verifiability are seriously lagging behind Wikipedia. Wikidata has not implemented WMF resolutions that the English Wikipedia has, and we are bound by them.