I don't think you can classify reading as a purely visual modality, despite being a visual medium. People with dislexia may see perfectly fine, but only the translation layer processing the text gets jumbled. Granted, we are not born with the ability to read, so that translation layer is learned. On the other hand, we don't perceive everything in our visual field either, magicians and youtube videos use this limitation to trick and entertain us, and these we are presumably born with, given that its a shared human trait. Evidently, some of the translation layers involved with processing our vision were seemingly evolved naturally and are part of our brains, so why would we not allow artificial intelligence similar advance starting points for processing data?