Okay, so I watched the following video It is called Autism meltdown or tantrum at the fair, so according to the title, Assa himself doesn't know.
I want to start with a little preamble. I offered to do this since Asa is an unreliable narrator and almost certainly has been from the get go. He is also often wrong (keep that in mind, I will come back to that).
The second thing is, no matter what it is, it doesn't belong on the internet imo. I find videos of toddler tantrums extremly cringy and no one wants that plastered on the internet forever.
Bit off topic, but the vlogs were way more pleasant to look at. They still dragged a little and had a lot of filler, but there were genuine attempts at proper cinematography. Also Abbie was pretty cute back then.
There are actually two tantrums/meltdowns in the video. The first one begins at four minutes when they arrive at the fair. And Asa was right, this was a plain old tantrum. Abbie disliked where they were and decided that she would rather not go. It is a drama in two acts. The first part is when she is told to put her shoes on. She whines and looks at her father before yelling. That is classic tantrum behaviour. A tantrum is meant for other people, to achieve a goal and convey a message. We all know the preschooler crying up a storm just to stop for a second to check if mum gave in and did buy the candy bar after all. the second part is after she didn't get her way (I know, I was surprised too) and had to get out of the car. She tried again, but calmed down remarkably fast when A&P mentioned food. She did shake her head, but that was just her being defiant.
The second tantrum/meltdown was at the fair (6:00). It is on "Abbie Cam", so there is less information. I want to take a little detour here and come back to Asa being wrong. He often describes a meltdown as a tantrum gone rogue (paraphrasing here), It starts out as a tantrum, but develops into a meltdown. That is incorrect, but I can't blame him here, because unfortunately childhood meltdowns and autistic meltdowns share the same name. But in reality they are very different. Asa describes a childhood meltdown. The kid whips itself into a frenzy and because it lacks the control and coping mechanisms of adults, it loses control and all hell breaks loose.
Autistic meltdowns are different. They are an involuntary reaction to overstimulation. There is no goal, other people don't matter. Autistic people usually try to self regulate or escape before a meltdown happens, because meltdowns are exhausting and you lack any control over your body and brain until it is over. It would actually worry me a bit if those two things were the same, since many adults on the spectrum experience meltdowns.
That said, in my opinion the second meltdown was in fact an autistic meltdown. Abbie tries to stim to block out the lights and people (handflapping, noises). She doesn't look for her parents, instead she hunches over. The reaction is more explosive. There is a cut, so I don't know how much time has passed, but when A offers her food, she doesn't react, instead she looks into the distance. When they get food, she is frowning and looking around. She also doesn't eat a lot.
This is all I got. Again, please take it with a grain of salt, since I have limited material to work with.