Well, as an autistic person, now I am curious. Was it lack of attention to his buddy, or what?
I cannot speak for Scott, but I think the experience I had with an autistic brother and sister can be helpful for the entire content of this thread.
It was an unusual situation to begin with. One of the shop's instructors was pregnant, and so she was scheduled to teach the classroom sessions of a class only, and another instructor and I (then a DM assisting classes) were to do the pool sessions. The first classroom session was Friday evening, and that instructor called to make sure we were prepared for what was coming. The class had 5 students. Two were typical adults. One had learning disabilities severe enough that the instructor had to read the test questions to him aloud. The other 2 were a brother and sister with autism. None of this had been told to the shop before the class. We were completely unprepared.
As you obviously know, when we speak of autism, we speak of a "spectrum," with some performing at an extremely high level. I am quite sure one of the scuba instructors with whom I worked was on the spectrum (Aspergers). My wife was then working in special education for the local school district, and she was an autism specialist. She knew of both the autistic brother and sister. The brother was much more severe than the sister. He required a full time aide working solely with him throughout the day in every class. In one of those school classes during the time we were working with him on scuba, he lost control in his music class and physically attacked the teacher, almost knocking him out. He was arrested for that. Their mother did not see any reason to advise the dive shop about any of this; she wanted her children to be treated like anyone else. Maybe her son needed a full-time aide in the classroom, but she wanted nothing like that in the scuba class.
The first pool session was a nightmare. After each skill, the boy would take his fins off and lay them aside. When we were above water, he would take his mask off and drop it. This alone made everything take forever. Meanwhile, the boy with learning disabilities was also struggling with all of it. Eventually, getting nowhere with the full group, we split the class into two classes meeting at different times, with the two non-handicapped adults in one group and the autistic siblings in another.
We got the first group through without too much difficulty, but the autistic siblings were a challenge. The instructor and I did two sessions with them alone, and we got about halfway through the standards. When we would be floating on the surface over the deep end of the pool, the boy kept taking off his mask and fins and dropping them, meaning I had to go down to the bottom of the pool, pick them up, and help him get them back on. I asked him why he did that, and he said, "So I can keep track of them." His sister was doing much better.
But they made progress. The instructor set up future sessions for them, and he said he could take care of those without my help. I don't know how many more multi-hour pool sessions it took, but eventually he gave the sister OW certification. He only gave the brother scuba diver certification, finally convincing the mother that he should never dive without the supervision of a dedicated professional.
The family was charged nothing extra. Neither the instructor nor I were paid anything extra.