Author: what [affordable housing] actually means: subsidized, rent regulated, usually awarded, housing.
HUD: Affordable housing is generally defined as housing on which the occupant is paying no more than 30 percent of gross income for housing costs, including utilities. ( https://archives.hud.gov/local/nv/goodstories/2006-04-06glos... / https://www.huduser.gov/portal/pdredge/pdr-edge-featd-articl...)
HUD defines affordable housing in terms of, well, its affordability. The author attempts to define it in terms of attributes secondary at best to affordability.
To the extent there's a discrepancy between the definitions of the federal government agency in charge of such matters and a random author on substack (who cites no source for their definitional claim), I'm going to go with the agency.