I don’t know if that is true, but there has been some fantastic studies looking at how text language helps young children learn to read. Lots of parents and teachers were worried that using text speak like ‘m8’ for ‘mate’ would stop children learning how to read and spell properly. Actually the evidence suggests the opposite. Text words like ‘m8’ help children listen to the sounds in words more. That means children can sound words out to read them.
So children’s thumbs may not be more developed, but there ability to read probably is! 😀