This isn't a miraculous step toward mind reading, I think, since much could be deduced about silent reading from subvocalization before. My understanding is that it is a very distinctive process.
We laugh hearing that the library of Alexandria was noisy with people reading the texts out loud, thinking 'how dumb were they?' -- just as they considered it a miracle when they came upon one who read silently. But though there is training the difference is slight; the advance to keeping one's mouth shut pretty much boils down to keeping one's mouth shut and doing everything else the same.
We laugh hearing that the library of Alexandria was noisy with people reading the texts out loud, thinking 'how dumb were they?' -- just as they considered it a miracle when they came upon one who read silently. But though there is training the difference is slight; the advance to keeping one's mouth shut pretty much boils down to keeping one's mouth shut and doing everything else the same.