Sorry this is long.
As a parent of two autistic young adults I'm finding this debate challenging - but I think it's important not to be defensive. I'm very aware of the comparisons with the trans debate and as GC feminist I really don't want to fall into the same trap many parents of sex dysphoric/gender non-conforming children have in terms of not being open to other explanations or theories for our children's pain/ symptoms.
I think my DC's story reflects the changes to the diagnostic criteria over the last couple of decades. My son and daughter were originally referred for assessment in the early '00 by the school ed psych when they were in nursery and primary school (completely unprompted by us) due to their atypical behaviours (DS - social/communication issues, stimming, hyper-sensitivity to noise, food issues, all consuming special interest. DD - developmental delays, lack of engagement, repetitive behaviour, unintelligible speech, echolalia).
Neither of them had melt downs or PDA. We called our DD our 'fairy child' as she was just quite otherworldly - appearing completely self-sufficient in her own world, limited 'sing song' speech, happy but often appearing completely oblivious to outside stimuli. (She has a NT twin so her unusual behaviour was perhaps even more noticeable in comparison.) Our DS hit all his developmental milestones - he fitted the 'little professor' description much more than his sister - early intense maths interest - but he was much more anxious, very literal and in a school environment had no clue how to 'play' or interact with other kids.
This was over two decades ago and at the time my son was diagnosed as having only 'traits' of Asperger's (probably because his interactions with adults were very good) a level of dyspraxia and executive function difficulties, my daughter was diagnosed with delayed speech and some attention and processing issues. They were given support sessions from speech therapists and ed psychs and other than being placed on the special educational needs register within school their childhoods continued in a fairly standard way - I think partly because they attended a very inclusive 'leafy' school that embraced individuality and had a strict anti-bullying policy.
It was secondary school that derailed them both completely - resulting in mental breakdowns, school refusal, therapy and medication. They developed debilitating co-morbidities - skin picking, emetophobia, GAD, clinical depression, suicide ideation. It was a horrendously difficult period for the whole family. Their senior school and university years were hugely impacted by their mental health struggles leading to a reassessment of their diagnoses in their late teens/early 20s - both were then diagnosed with the new label of autism.
But the thing is - they still got to university - one of them has a PhD. They're both employed - although part time due to their health needs - and although they both still live at home, they could, with support, live independently in the future. Their struggles have shaped their social lives and career choices meaning they may find it harder to meet partners and their jobs don't reflect their academic potential or creative abilities - which feels like a waste of talent but at least they have agency over their lives. This is completely different to the next generation of children being born into our extended family who have 'classic' autism, are non-verbal, incontinent, can't attend mainstream school and may never be employed or live independently. Probably because of witnessing this, both my DC feel the current 'autism spectrum' label is too broad and an Asperger's diagnosis would more accurately reflect their daily challenges compared to their cousins.
The only other thing I would say is, I really hope this debate doesn't play into the hands of those just wanting to justify reducing the already limited support higher functioning autists can access. Someone up thread talked about 'stealing' support from the less able/ more vulnerable. There really is very limited support for higher functioning adults as it is - my own children have found it practically impossible to access any meaningful support once they aged out of CAMHs - 90% of their support has always come from family anyway. The main benefits for them of a diagnosis has been a greater understanding of themselves, improved self esteem and the legal protection to ask for reasonable adjustments at work if needed. This hasn't cost the tax payer very much at all.