Technical an common language often intersect in logically confusing ways.
Blindness is on the greater vision spectrum but not all of the vision spectrum is the blindness spectrum. At a point on the vision spectrum one stops being blind and becomes sighted. Think of it like light. Ultraviolet is on the light spectrum and has a spectrum of its own; but not all of the light spectrum is ultraviolet.
ATMs give out $20 bills. In order to get one back as change you'd have to pay with a bill larger than $20. I don't remember the last time I carried something larger than a 20.