This is one of the few disputes where the atlas can say precisely what is being argued, because both sides have set out their case in print.
The case for doubt
No document of the sixteenth century names Juan Diego or describes the apparition. Juan de Zumarraga, the bishop in the story, left a substantial body of writing and never mentions it. The Franciscan chroniclers of the early Mexican church, including those hostile to the Tepeyac devotion, are silent about it. Stafford Poole set the case out at length in 1995. The earliest accounts date from 1648 and 1649, more than a century after the events they describe, and the tradition of Juan Diego cannot be traced behind them.
The case for the defence
Defenders answer that an absence of documentation is what one would expect for an indigenous commoner in the first generation after the conquest, that indigenous oral and pictorial transmission is not the same thing as a paper trail, and that earlier documents do exist. The most discussed is a small pictorial manuscript bearing the date 1548 and the name Juan Diego, which surfaced in 1995. Its authenticity is itself disputed.
What happened next
He was beatified in 1990. In 1996 the abbot of the Guadalupe basilica said publicly that Juan Diego was a symbol rather than a person, and left his post. In 1998 a group of historians, Poole among them, wrote to Rome asking that the cause be reconsidered. The canonisation went ahead on 31 July 2002.
The atlas records the dispute rather than settling it. What is not in dispute is the devotion, which is one of the largest in the Christian world.