There's a maturational thing that has to happen in a brain before the visual/attentional system can figure out what to do with all those little loop-de-loops on the page. Age 4 is simply too young to be deciding it's dyslexia. More likely, he simply isn't reading-ready yet.
I agree. But I would also advise to read
The Dyslexic Advantage: Unlocking the Hidden Potential of the Dyslexic Brain
so you can understand FIL better.
I know that Dyslexia isn't generally a visual problem, but it sure is worth it to check his visual system, both with a standard Optometrist, and a Behavioral Optometrist. It took a bit of extra time for my son's visual system control to mature, and his reading just didn't click in until late kindy/early first - in spite of knowing the letters and letter sounds at age 2! I sure wish I had had a place to post about that way back then - it was scary.
Love and More Love,
Grinity
