I have had quite a fair few kids over for tea during these holidays and if they get down from the table without asking then I will request from them that they ask before they get down as this is what we do in our house.
Today I have my nephew over to sleep, he kept getting down from the table and trying to play when we were still eating( he is 3yo)
so I asked him to stay sitting and to ask if he wanted to leave, he wouldn't ask, he refused so in the end I just said ok then but next time please ask.
AIBU and old fashioned? And I am expecting too much of my nephew (FWIW i also have a 3yo DD and she asks and has asked since she was out of a high chair)