I've been thinking this for quite a long time now, and while I know it doesn't make outright sense, but please take a minute to digest this question.
Consider the definitions for "disability" given by popular websites:
a physical or mental condition that limits a person's movements, senses, or activities.
OED (second edition)
a. Want of ability (to discharge any office or function); inability, incapacity, impotence. b. An instance of this. (Now rare in gen. sense.)
Disabilities is an umbrella term, covering impairments, activity limitations, and participation restrictions. An impairment is a problem in body function or structure; an activity limitation is a difficulty encountered by an individual in executing a task or action; while a participation restriction is a problem experienced by an individual in involvement in life situations.
A disability is a permanent injury, illness, or physical or mental condition that tends to restrict the way that someone can live their life.
I have a specific reason for why I think the above three definitions are wrong. The reason is that they are mixing up incapacity along with disability. Incapacity is an umbrella term to refer to any kind of non-ability in any regard, eg: incapacity to cast a vote in elections, incapacity to walk on two legs, incapacity to lick your elbow, etc. Oxford defines it as:
Physical or mental inability to do something or to manage one's affairs.
which matches nicely with the above examples. However, I believe disability is specifically a term made for referring to activities which a normal person can do while the affected ("disabled") person cannot. These websites get the definition right the way I wish it to:
a physical, mental, cognitive, or developmental condition that impairs, interferes with, or limits a person's ability to engage in certain tasks or actions or participate in typical daily activities and interactions
A disability is any continuing condition that restricts everyday activities.
an illness, injury, or condition that makes it difficult for someone to do the things that other people do.
Certainly, licking your elbow is neither an everyday activity nor what other people do. thus it makes absolute sense to not define it as a disability.
Having clarified my question, I wish to ask if: (1) the aforementioned dictionaries have wrongly defined the term "disability" (2) I have incorrectly interpreted the otherwise correct definitions.
I am a learner of English and have tried to post a properly structured question, so please consider clarifying in comments in case of confusion.