From an evolutionary perspective though vision had millions of years head start over written language. Additionally, almost all animals have quite good vision mechanisms, but very few do any written communication. Behaviors that map to intelligence don't emerge concurrently. It may well be there are different forms of signals/sensors/mechanical skills that contribute to emergence of different intelligences.
It really feels more and more like we should recast AGI as Artificial Human Intelligence Likeness (AHIL).