I'm saying that if you find out you're going to have a disabled child and you think, "How will I take care of this child once it becomes an adult?" and then you think "Oh well I'll just make sure it stays a child," especially if this is followed up by any sort of thought similar to, "I'm so glad I'll be able to hold my child in my lap forever!" maybe you shouldn't have the child in the first place instead.
The point here is not about disability. The point is about parenting.
I find the idea of parents unilaterally altering their children in permanent and significant ways in order to make their job of parenting easier pretty revolting, and "but the child is severely disabled" really doesn't do much to change that opinion. When you add a serving of "Now I'll always be able to treat them like an infant," you've completely lost any ground you might have won with "but they're disabled!"
Definition of disabled? Up to the parent thinking these thoughts. I also accept adoption or other similar methods as options which qualify as "choosing not to have that child," for the squeamish.