The kids could have ASD, but since it only affects 1% of the population, there's a 99% chance they're just typical kids absorbed in technology.
My dcs are part of that 1%. And I'm tired of people making judgements about them when we're out in public. Perhaps people could just simply give others the benefit of the doubt. Or mind their own business. 
When I see people out with their kids doing this I thinks it is lazy parenting, easier to put the head phones on and switch off than getting involved with them.
Lazy parenting might be not bothering to take the dcs out at all in my house. Taking the dcs out is an enormous undertaking, as it takes tons of patience, preparation, and work to get ds1 through a public meal. His coping skills in public places are minimal, mainly due to sensory problems, and in restaurants he is pushed to his limit. But if I never take him anywhere, he would become a hermit, which I suspect would also be considered unhealthy. More judgement then. Not to mention his brother needs to go out of the house and experience things as well. So we struggle through meals in public sometimes, using headphones or an ipad or whatever it takes to allow him to cope.
But for as long as we put up the sn argument on every thread we are stifling the point of the thread which is a debate.
There is something to be debated here: the use of gadgetry at a table to excuse each other from actual communication. Which I think is pretty appalling, I don't care how end of tether the woman is, surely the lot of them could have unplugged themselves while eating?!
Debate all you like, but I still feel that it's important for people to be open minded enough to recognise that for some, it may be a necessity. The "sn argument" as you so charmingly put it (quite neatly tying us up in a little package and dismissing us as negligible IMO) is denying the fact that people with disabilities and special needs are part of society. Kindly don't be so quick to dismiss them. They matter. And let's show a bit of compassion - perhaps there aren't any SNs involved, but one would think you could possibly sympathise with the idea that perhaps the mum is struggling and needed the down time. But hey, no, even though her kids are quiet and not bothering anyone, let's find some sort of stick to beat her with anyway. After all, we "don't care how end of tether the woman is" do we?
As kids, we were never allowed to read books at the table, no matter where we were eating; how is this any different? It's basic manners.
I wasn't allowed to read at the table when growing up either. And my dd wasn't. However, now that dd is an adult, and ds1 has disabilities that means sometimes he struggles, especially in restaurants, I am prepared to bend the rules in order to allow him to cope and to keep him from causing a disturbance that might upset other people in the vicinity.
So nice to know that if I don't give him the tech stuff or headphones, when he makes noise or has a meltdown, that people will judge. But if I give it to him, people will STILL judge. And people wonder why we feel attacked and singled out? Seriously? It doesn't matter what we do, people seem to feel that we are wrong... oh wait... people are never on here judging parents for not taking their child with disabilities or SNs out in public... interesting, isn't it?