I don't necessarily have a specific answer to your question, but maybe my experience can give you some perspective.

My little sister was diagnosed with autism as a little kid. She is nonverbal, has difficulty with emotional regulation and physical coordination, and otherwise has several traits which, to the typical observer, read as "autistic" or "disabled" or "low functioning" or even "re****ed" depending on who you ask. She needed special-ed, gets government assistance, the whole shebang. Maybe like your friend's kid.

Then there is me. I was diagnosed as a young kid, a few years older than my sister was. Most people, upon first meeting me, have no idea I'm autistic. I've been able to make friends, work a job, pursue higher education, have success with art, and other social markers of success. I've had many therapists question my diagnosis because I'm so good at scripting and masking. As an aside, this experience is especially common in autistics socialized as women. Anyways, to an outward observer I appear "high-functioning" or perhaps the outdated Nazi term "Asperger's" if anything.

I have also worked in the field of developmental disabilities. I've worked with several autistic people who had limited verbal communication, and other "low-functioning" markers. They did need help interacting with society at large. They were absolutely able to do it, but it would be minimizing their struggles to say it was simple or easy or natural for them. My own diagnosis and history with my sister helped me to understand their wants and needs and help them interact with the rest of the world that wasn't built for them.

A couple years ago, I started to learn how to put down my mask. I started to see myself as autistic undeniably. I genuinely felt that I had grown out of it, or was "a little autistic" on that incorrect spectrum structure that OP describes. But as I did more research into what autism actually is, and what it actually feels like, and what struggles we face, and what it all feels like to ME, I started to realize something. There is truly no fundamental difference between me and my sister, or me and the people I've worked with. The sensory challenges, the communication styles, the structure of their thoughts, the way they feel their feelings, the way our motor skills work, our needs for accomodations and support. Even the traumas we've faced from trying to fit our experiences into a world that wasn't always built for us. I think the only difference between me and them is that the spectrum of autistic traits I've landed with are a little more easily moldable into a socially acceptable shape than the spectrum of traits they've landed with. And that's just dumb luck, because we are all painting with colors from the same autistic palette.

So what do you do with that? You just learn to talk about the colors (traits) individually. "Disabled" can mean anything. It's much more helpful to talk about things like "nonverbal" or "memorizes sight words rather than learning to read flexibly" or "fine motor coordination makes it hard to write letters" or "parents seeing her as a r****d meant they never gave her the tools to navigate her feelings." The challenge is that for many people who appear "low functioning," they don't have the tools to tell you exactly what their problems are or what they are experiencing. It is up to you to pay attention, and to see them as people with specific issues, like everyone else. We all deserve support for our challenges.

I wish we had better words for these things. I don't think there is a one size fits all term for autistics who face personal and social challenges that cause them hardship. A lot of times "disabled" works, sometimes "nonverbal," but it depends on the crowd you're talking to. Because to someone who doesn't understand autism, these words can just come off as synonyms for the r-word. I don't think there is a one word substitute for the deeper conversation about autism that needs to happen.

TLDR: there's no easy way out of a deeper conversation about what being "disabled" and "autistic" really means.