Yes I was interested in this myself so, before posting what I just wrote, I looked into it and went through the sources on a few papers. I ended up at this fairly authoritative-sounding book which made the claim, though I don't remember the source they cited and I can't be bothered to find it again. The claim made was not that dyslexia wasn't present in other languages, but that its effects were reduced in phonetic ones. The same way that someone in a wheelchair still has broken legs, but can benefit greatly from the installation of ramps.