The child you described is HF if he has an IQ over 70. The fact that people misuse the term makes communicating about autism more difficult.
Do people even realise low and high functioning are completely arbitrary categories?
How could a person who needs 24/7 care be described as "high functioning?"
I would ask you to link to the criteria for high or low functioning autism, but I won't bother because I know no such thing exists. Neither are a proper diagnostic term, merely an informal one which is used and twisted to suit whatever the person using it wants it to mean.
All of this demonstrates how stupid functioning levels are, the fact you call a person who is severely autistic, non-verbal, needs constant care, was diagnosed before age three "high functioning" just because he has a normal IQ. That illustrates perfectly how pointless such labels are.
You're not exactly correct, true verbal ability isn't part of the diagnostic criteria, but the three levels of ASD (which are meant to represent levels of severity) do mention language development, or lack of it. Also the new DSM says each diagnosis should note if a person has autism with or without learning difficulties, thus making it clear they are not an integral part of autism. There's not much I do like about the DSM changes but that is one of them.
Level 1 is meant (in theory at least, because personally I think this system of levels is just as bad as the whole low/high functioning thing) to be the equivalent of Aspergers and the wrongly used term HFA. Its supposed to be the people who need the least help. So I guess the DSM disagrees with you. The level 3 description clearly mentions people who have no or little speech. And level 1 refers to people who are very articulate. My point is there's no way someone with his needs would be described as having "level 1 autism" aka HFA or Aspegers.
Why does the term high functioning autism hold such currency when it's no use at all? Like I said the DSM gets that right at least, simply noting whether or not a person has learning difficulties or not. Because the terms high and low functioning don't tell you anything about that person and the impact their autism has on them.
www.verywellhealth.com/high-and-low-functioning-autism-260599