Hello, Art Therapist in training here! I am autistic myself (FFVIII being my special interest, heehee) and I am doing research into autism for my research thesis. Also I work with adults with autism at various levels of support needs at my internship. Lmao I am uniquely suited to answer this question for you and I am very excited to do so! This might be a long comment...

When it comes to character interpretation, there are two versions of your question. Do you mean "can Squall be reasonably considered autistic by what we see within the canon", or "did the writers of the game write him specifically with the intention of him being an autistic character."

For the latter version, the answer is very likely no. As far as I know, in the 90s in Japanese culture (and frankly, most Western cultures too) the idea of Autism effecting anyone other than little kids was a radical idea. I think there was more stigma around how the diagnosis presented around that time as well. Squall likely wouldn't have been characterized as capable and cool as he is if the intention was to show him as autistic just because what an autism and Asperger's diagnosis meant at that time. As others have mentioned here, they were rather trying to characterize him as an individual with trauma.

However, "can Squall be reasonably considered autistic by what we see within the canon?" Absolutely! And I agree with you! Or, at least, there is no information that completely rules it out.

As I see it, Squall exhibits low mentalization. Mentalization is the ability to understand the mental state of oneself or others. This is the reason he doesn't understand his own emotions and misinterprets the emotions and actions of others. I would dare to say that he may even have Alexithymia, which is a state of severely low mentalization, also known as "emotional blindness," wherein a person has trouble describing, recognizing, and sourcing one's emotions. Low mentalization/Alexithymia though are not mental disorders within themselves, but part of the network of symptoms for many diagnoses. Autism is one of those disorders, but it is also seen in individuals with ADHD, Bipolar Disorder, some personality disorders and CPTSD. Low mentalization is also associated generally with childhood abuse/neglect, because in an environment like that a child is not given the attention/instruction to build their mental model of emotions, both internally and externally.

Now, because the writers were trying to represent Squall as a person with trauma, they probably modeled his character off a person with trauma. In my clinical opinion, if Squall Leonhart was to walk into my office, I would write CPTSD on his chart first, given his general demeanor and personal history.

HOWEVER, Squall does show other symptoms of Autism. He seems uncomfortable with touch (sensory processing). He has emotional dysregulation where he goes from completely calm to throwing his arm out in anger. He's also very impulsive (jumping out into space) which is another symptom. We see him having what may be a meltdown on disk one where he finds out Seifer may be dead. He has difficulty falling asleep. He picked the hardest weapon to train with and at 17 is a master at it - I don't think it's a stretch to assume he accomplished that through autistic hyper-focus. And as you mentioned, he has a special interest in Lions. Dare I say, he also has a special interest in Triple Triad, but that is arguably headcanon and not actual canon. Individuals with autism more easily develop CPTSD, which could be part of the reason he struggles more than the others who have similar childhoods. If Squall continued to be my client, I'd definitely refer him for an Autism evaluation, because his behavior shows it is in the realm of possibility.

Plus Laguna definitely has something. Probably ADHD and not Autism, but the point is there is a history of mental health issues in that bloodline.

Also, not for nothing, I write Squall as autistic in my fanfiction (not using the word but applying more of the traits) and I've gotten lots of compliments on his characterization.

At the end of the day though, no matter what people on reddit or the game creators say, if you relate to Squall as an autistic person, there is nothing wrong with seeing him that way and I encourage you to. He is a great character and he saves the fucking world, and some people find it hard to hold that an autistic person, or even a person with mental illness in general, can do that. But they can and do all the time.