Thank you all for your replies. This is quite an eye opener in some ways. Probably because I've mainly had discussions around severity previously in forums/ groups for parents whose children are classed as such.
It is a term we're used to. It's helpful because it does go some way to distinguish between someone with a dx who has just a few deficits/ on certain days/ in certain situations to explaining that the "severe" side has them all/ all the time.
I chose the a word to compare as this seems the most severe person I can think of with autism who is in mainstream media. I did not choose rainman as that is a different dx but rainman is more like what I deem severe. Headbanging, smearing, rocking, flapping, challenging behaviour, very limit communication, no personal skills, help to dress, brush teeth (if tolerated), go to the toilet, can't be left alone for any time at all.
Autism is not autism, Chris Packham et al are a million miles away from what I recognise as autism. Autism is far from a gift for us and I would remove it from my child I need the same way I would want to remove anything which hinders him and stops him living his life. For us it s a disability.
I think the labels help in the same way we distinguish people who have leg injuries. Not all leg injuries are the same, a broken nail is completely different to amputating. Different in impact and required levels of support.
I think the labelling is adverse to people who can function but helpful to those who can't. It helps to communicate level of need and support.