The claim isn't absurd if one takes the entire sweep of topics covered by wikipedia: it's generally solid on mathematics, fundamental science, ancient and medieval history, art, music, or in any portions of other areas that have not been politicized by the Left. Once one hits the Age of Discovery, history starts going to heck, and it gets worse as one approaches the time span within the historical consciousness of the woke. Probably most articles are sound. It's just that it's a terrible source for anything that bears on public policy, social commentary, politics, or contemporary culture.