Common thought, but not really true. The basics of accessibility might be considered just "usability" or even UX, but going beyond that, it steps in being useful for people with certain disabilities while not impacting people without.

One example from the article, `aria-hidden="true"` (https://www.w3.org/TR/wai-aria/#aria-hidden) might be used to hide elements containing text that are not useful for people with screen-readers, while not changing the experience at all for the ones not using one.