No he wouldn't understand that, zzzzz
The talker while clunky is helping his communication a lot, and he has picked up how to use it very quickly. The ed psych was talking in terms of him learning keyboard skills and using the talker to help (even as far ahead as GCSEs)
He is just starting with phonics really, on level 1+ ORT books, with a sentence like ' dogs like to run' (this is one of his favourite books, so he may be able to read it because he knows it very well!) when he sounds out the words, you can tell when he knows the word, even if he can't say the word clearly (he will sign it, or find it on his talker) if he doesn't know it, he will look at you for help.
If you remember he was very very anxious about separating from me, and he has made huge leaps with that, But still needs a lot of preparation for change, like being picked up from a different classroom. The thought of sending him on transport to a school miles away with none of the children he recognises seems huge.
(By the way, thankyou zzzzz
hope your brood are all well)