I don’t remember that. DD1 was in special language provision from age 4, over 25 years ago, until she was 16. There were always children with autism and speech/language disorders in her class. The autism was quite subtle in most of her friends - certainly not the severe form. I remember one of her friends had a diagnosis of PDDNOS. Her specialist speech and language school said, 40% of their intake were on the autistic spectrum. Their view was that their language tended to be better than the language disordered children, like DD1, which was a good model for them; but the language disordered children had better social skills, a good model for the children with autism. However, the school had to be careful not to become top heavy with autism, as that didn’t work.
There was a lot of discussion around that time about the overlap between SLI (specific language impairment), as it was then and autism, especially about semantic-pragmatic disorder (now iirc usually called PLI or pragmatic language impairment). Some people believed all children with semantic-pragmatic disorder were on the autistic spectrum, while others believed some children were and some weren’t. I regularly heard from mothers for instance that she’d taken one of her children to Margo Sharp for assessment, but not only had that child been diagnosed the autism, but the father and older brother had come away with a diagnosis of autism too! It must have been subtle, as the severe form would have been obvious!
I never came across the automatic assumption a child with speech or language disorder was autistic, until I came on MN much later. We were always told the incidence of speech and/or language difficulties in children was ten times higher than autism (although the incidence of that has been revised from the 1 in a 100 back then).