I think the connection with AP and sippy cups is
that children who are breastfed on demand, and experience child led weaning have less need for sippy cups. This is not to judge anyone here, but just to explain the possible connection in some families. In my family, we never depended on sippy cups for this reason. My kids dont drink much cows milk,
we only have juice for breakfast, and therefore only need cups to drink water. Usually when out, both kids just drank from my water bottle. When the baby was too young, he tried carefully from my bottle, and i provided his own little cup (not sippy) with a little water in it. That cup was used for other purposes too. The other reason i didnt use sippies is i find them unhygeinic. But thats because i dont have a dishwasher and cant wash them properly. I think all of these things are tied to a life style that is dependent on things lke dish washers, cars, etc etc.
I got my kid a sippy cup one day because he saw another kid with it in the playground, and seemed to really like it. But we didnt use it much, although we had it. Sometimes he requested it specifically, and I got it for him. I had some others too, but usually take off the top. (convenience more than anything) On the other hand, i can see that sippies create less spills, so i guess im cleaning up more spills.
As for high chairs, i feel the connection to AP is that a) it creates separation,(not on lap) but then it can foster community too (kid can sit at table with adults) b)I dont like the idea of tying someone down, and for the baby not to have freedom of movement. Yes, its easier for the parent, but it just goes against the grain for me.
Also, the notion of tying a kid down to kind of spoon feed goes against the grain. I prefer to give the child freedom to pick from my plate.
Bottom line though , for me, was lack of space, so i never used a high chair. Also, both my kids were climbers and escapee artists, and wouldnt have put up with it for long.
Also, because of this they learned to sit up and have more control at an earlier age than other children i observed, so outgrew the need for a high chair faster.
Generally, we share food from the same big plate, and even drink from the same cup (saves on washing up for me) and also fosters connection and communtiy. I never had trouble getting my kids to sit at the table for a meal. Thats just what we do. Don’t know if its because of this. When kids asks for his own plate, or cup, he gets it. Now he’s 4, he generally gets his own plate, but sometimes we still share from mine.
So, high chairs and sippies, they can be what you like. But i do think that sippy cups aid in the weaning the child. I dont think they have to be non AP though, just explaining how i see it, and how it worked for me.