Yes. I saw that too.
I’m not sure what he’s talking about. It may be a typo. He may have meant to say that Arab children read *numbers* from left to right – and this is true. I’m not sure why this is, although it could be due to number symbols and decimal notation were both adopted from India and all Indian languages are written from left to right.
Whatever the origin, Arab children learning to read need to parse symbols in both directions. Something else he does not mention is that even Arabic letters flow right to left since they connect or do not connect differently to adjacent letters, whether on the left of the right.
This means that the letter itself contains information about it’s correct direction. This is not the case with Latin based alphabets, Greek, Hebrew, or or any other Semitic language other than Syriac (a dialect of Aramaic with it’s own writing system). It is probably an innovation of Syriac, which appears to be the origin of the Arabic writing system.