1.3.1 Info and Relationships
Have you ever complained about developers who don't know a damn thing about semantics? Labels that aren't associated with their form fields, headings that don't use <h#>
tags, tables that aren't tables, shit like that. Well, this is the giant-ass umbrella criterion for you. Every fucking piece of information or relationship that you can infer visually has to be present in your goddamn code.
Doesn't matter whether you use HTML or ARIA, Info & Relationships doesn't give a shit. Just spend a tenth of the time it took to choose the perfect heading font no one cares about, and make sure blind people can skim your content as easily as the sighted people whose eyes are bleeding from the joy of that perfectly kerned slab serif.
Semantics. Use that shit.