The reason it is often called the "T21 movie" is because the climax of the film takes place at a location labeled (a mall/complex), and the intricate plot involves the protagonist using the building's architecture and timelines to solve a crime.
Here is a solid review covering the film and an analysis of the emerging "T21" genre in cinema. t21 movie
Disability advocacy groups, including the Down Syndrome Diagnosis Network (DSDN), have issued statements urging viewers to avoid the T21 movie. Their concerns are threefold: The reason it is often called the "T21