:up: It's a jocular analogy, poking gentle fun at politically-correct shibboleths like 'You mustn't call people who can't hear "deaf"; you must call them "hearing-impaired".' A similar thing is done with the expression 'coronary bypass'; someone with no sense of humour is sometimes said to have had 'a humor-bypass' (no typo, this strikes me as an American sort of joke).
b
PS I know I know I know already: 'hearing-impaired' covers a range of abilities ranging from hard-of-hearing to deaf-as-a-post. But there is a knee-jerk reaction in many contexts to replace 'deaf' with the euphemism, just as 'OAP' [=Old Age Pensioner] has been virtually extinguished by the importation of 'Senior Citizen'.