they all seem to have in common the idea that it's a disability or difficulty

That is a remarkable insight, and it has ramifications far beyond reading scores and the ability to catch a ball.

My definition of 'Dyslexia' does not appear to tally with the strict 'learning difficulty' definition that is presented by that Wikipedia article in confident tones and strictly-defined terms of one's ability to acquire reading skills at school.

Nor do I recognise much of what I know - or thought I knew - in the 'magnocellular theory' section, which is Wikipedia's only concession to the view that dyslexia is a broader condition which presents a notable symptom - poor reading scores - among other less-obvious differences from the statistical norms of the general population.

So what follows is a purely personal view, a series of anecdotes and a precis of the discussions following a fellow-student's third-year clinical psychology project, twenty years ago.

At that time, clinicians had noted that dyslexic children presented other symptoms: the inability to catch a ball, balance problems or dyspraxia, poor performance judging distances, 'cross-lateral' phenomena, difficulty with names and - frequently - other cognitive or memory-based problems that have a common theme of somehow failing to link things with other things.

When studied more closely, children and dyslexic adults that had been educated in a sufficiently rich environment (not always true of children regarded as 'dull' because of their reading problems) were found to have abilities that challenged the notion of dyslexia being a 'disorder' or 'learning difficulty': visual recall, spatial skills, an innate ability with 3-D visualisation, logical and analytical abilities that are nowadays highly-prized among database developers. Some of it (like my hoover-like appetite for lexicological trivia) grow out of adaptations to the 'words' deficit; others are innate gifts and valuable skills.

As in all psychological diagnoses, the researchers (and clinicians familiar with the work and unencumbered by ideology or mechanistic diagnostic methodologies) saw that there was no 'definitive' case: one person could have one, or some - but rarely all - of the signs and symptoms. Some, like poor distance-judgement, would seem to contradict others - like the exceptional spatial skills observed in a majority of 'dyslexic' teenagers.