"Dyslexia" is, as McGrath said, a label, not a diagnosis. As to whether it is "a looad of bolux, no sutch theng", I can only offer a personal anecdote. I have three children. Both my wife and I read to and with them for an hour or two a night, not only pre-school but we were still doing so when they were nine and ten. My eldest son and my daughter had both finished every book in the primary school within two years of starting - we had to send them in with more demanding material. My middle son - same home life, same school, same teachers - was still unable to distinguish any of the 'wh' words (why, what, when etc) by the time he was eleven. On every other assessment, he scores highly. For example, an assessment of his vocabulary put him in the top 5% of his age range - the limit of the test. Similarly, IQ test, verbal reasoning, etc, etc.

He has no difficulty reading a musical score, by the way.