Oh, it's one of those "diagnosed with dyslexia" top trumps games, where someone cuts and pastes a list and hope no-one either checks or knows why it's mostly wrong. I can tell, by the way, that it's cut and paste because I seriously doubt that you have the career of a minor American TV presenter of DIY shows, the equivalent of Handy Andy, at your fingertips.
To take the most egregious examples, Winkler has a BA from Emerson College and an MFA from Yale School of Drama. Jay Leno likewise has a degree from Emerson (it's a fairly big deal on the east coast, kind of a combination of St Martins and RADA).
Billy Bob Thornton started, but did not complete, at a four year liberal arts college (ie, a university). That means he must have at least graduated high school and achieved a decent SAT result.
Orlando Bloom attended academic private schools, and completed A Levels.
Knightly started A Levels in English Lit and Classics and, as her IMDB bio says "She was not officially dyslexic as she never sat the formal tests required of the British Dyslexia Association. Instead, she worked incredibly hard, encouraged by her family, until the problem had been overcome by her early teens." I can imagine there's quite a lot in there to annoy people who work in dyslexia.
And in any event, given her mother's a successful actor and writer and her father a successful actor it might be a little hard to draw strong conclusions about much of her career. Likewise Charley "son of John" Boorman, who again attended academic private schools and did A Levels.
Cruise went to a seminary on a church scholarship, which implies a fairly high level of literacy.
Vince Vaghn graduated from what, by American public school standards, is a very academic high school (SAT mean scores of 600 in every section, so a mean SAT score of over 1800? I know people who've taken the SAT from super-selectives in the UK and not got remotely close to that).
I'll give you Susan Hampshire and Keanu Reeves.
So let's rephrase that. "If your father is extremely rich as a director of a multinational company able to fund your mother opening a school solely for your benefit, or you're one of the most beautiful men of your generation, then lack of academic success is not necessarily a bar to becoming an actor".