So how does iPad actually helps? How is this different to writing or typing on a typewriter. I also form words from letters, and sentences from words while typing or speaking.
There's plenty more to it than just writing and typing, but let's focus on that directly, for just a minute.
Look at Dillan's hands and mannerisms in the video. Now, imagine handing Dillan a pencil and piece of paper, and insist on the fine motor control that handwriting would require. Actually, we don't need to really imagine it, because it's happened to people like Dillan before, and sometimes even happens to this day. The situation ends up very frustrating for them, and it's compounded when people around them just assume that a lack of ability to manipulate a pencil means a lack of intelligence.
Typewriters: Have you tried typing with one, or carrying one around? Even the electric and electronic models have their limitations. They are heavy, clunky, loud, and very unforgiving. Even someone like me, who has typed on computer keyboards for most of my life, would dread having to use a typewriter. It would be a frustrating experience I'd want to avoid, and I'm sure you would too, unless you're a glutton for punishment.
I suppose a laptop would probably work okay, but even that can be cumbersome in a lot of situations.
Or, you can hand Dillan a 1 pound tablet with customized software, that can accommodate for his writing patterns, predict text, even compensate for tremor and motor control issues.
This type of interface you can't find on a typewriter or pencil/paper, and would probably be inefficient on a laptop.
And to be fair: Yes, specialized tablet-like equipment did exist before iPads to enable communication like this. However, it was expensive, slow, bulky, and single-purpose. This is way superior to what was around before this.
And let's be blunt here: it's a technological advancement that makes things immensely easier, even for those of use without autism. I mean, why do
any of us bother with iPads and computers, when we could get along just fine with slate tablets and chalk, right?