Yes, the technique is cruel.
Basically, it involves taking kids, giving them 'good' feedback - eg, access to a toy - if they mask, or act like they are not autistic. It gives them punishments, which in some cases is electric shocks if they misbehave - which can mean anything from not making eye contact to lashing out because they cannot get the bad things to stop and they need it to stop. Other common punishments include forcing kids to touch or smell things they dislike.
A common reward is something like getting your tablet back. Many autistic people are nonverbal, so they are removing their ability to communicate and expecting them not to try communicating by, say, lashing out or having a meltdown when the bad things keep happening.
The goal of the program is not to help, as therapy does. It does not allow them to explore possible coping mechanisms, eg headphones or fidgets, to find ones that work well. It says that their autism - a facet of who they are - is bad. They do not allow autistic children to stim, or repetitively do an action. While some stims can be bad (eg my childhood stim of picking at my skin), that is not because stimming is inherently bad but because the particular mechanism is bad. The way I stopped picking at my skin (mostly) was by redirecting it, eg by using fidgets or by finding something that feels the same but is less harmful. (I'd be getting my fingers covered in kid-strength glue a lot more often if it wasn't inconvenient.) Stimming is important for coping with stress and regulating emotions. Plus, they're enjoyable.
ABA also leads to nearly 50 percent of people who are forced to undergo it having PTSD. (Autistic people are at a higher risk for having PTSD, but it is still a marked increase.)
It is child abuse, plain and simple. There is no possible justification for it, and it is absurd and terrible that when it is being inflicted on autistic children it turns from child abuse into 'therapy' and gains any measure of acceptance.
A great resource on it is here: https://autisticselfadvocatesagainstaba.wordpress.com/2020/0.... A fair amount of the specific details of ABA are from here, as I - thankfully - have not undergone ABA. (If you want a more reputable source than random Wordpress blogs, the Autistic Self Advocacy Network [https://autisticadvocacy.org] also condemns it.)
Also, when over half and possibly nearly 9 out of 10 autistic women have been sexually assaulted (!) [see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9087551/], teaching kids that adults can touch their bodies how they want and they don't get a say in it might not be the best idea.