Op a few things to consider, do you think your friend knows her dc better than you?
Do you think bar the two hours they were with you sat glued to their screens, your friend does in fact interact and talk to her dc? Or do you feel this is a an by hour daily event in their lives.
Its just that - my 4 year old wont sit and has never ever sat nicely at a table, she has never been strapped in, she never took to a high chair, pram, airplane seat, even her car seat she has fought and fought to be out of it.
My 4 year old is also whilst a lovely little girl, very very active, eating at a restuarant has been something we have been able to do actually, and on holiday the only way we can get her to sit - and literally let us take our eyes of her for a second has been to give her her tablet. However we lead very full lives, they do loads of actives, are out at museums, woods, NT houses mostly both days on the weekend.
We also have an older DD who has beautiful table manners and can more than hold her own in conversation she is now 10. She was similar to DD2 but not as bad, so - we have managed to turn out a young lady who can talk, and interact with other young people but also highly educated adults.
i don't find this country to be very accommodating of young children and the only time out and about I have fully relaxed has been in places like Italy or Spain. This is where people don't wince when a child cries when they are out.
Its a bit of a loose loose situation. We don't inflict our younger DD on people in restaurants, not fair on them and no fun for us, and on the very odd occasion we have, after the rubbish crayons and colouring have run out - given her her tablet to watch something on, its the only way for us. To buy us a few moments of peace. We have no family support system all sadly passed away, and no money to pay for baby sitters.
It makes me sad people like you are looking over and judging us, but at the same time I would like to see my older DD compared with your Dc - chatting at the same high level of discourse.