Oh dear, I can imagine what all the GN's would have thought of me at that age. I think what he did was perfectly natural and very good to feel at ease with his extended family. As an eldest child I was put in the position by my parents of being responsible for my younger siblings, to the extent of being expected to explain to any adult, that "my sister needs the lavatory" or " He cannot eat a cheese sandwich, cheese makes him ill" . So this meant that I was quite used to speaking to adults, and didnt see this as anything unusual. I lived quite close to my granny and to my great grandparents, and saw them regularly. So I grew up expecting them to be able to answer my questions and help me with anything, and at the same time, naturally would ask if they needed anything fetching or remind them their glasses were still on the table.
It is a mixture of your own nature, and what you are used to. The covid situation certainly has made a difference for everyone, and no doubt due to those circumstances , children would be more isolated or mostly being with a limited group of adults and not have been having that rough and tumble getting to know larger groups of children, where they see what is considered "natural" behaviour for children.
So well done to the little boy and to his parents for a polite and thoughtful effort. Surely , while you might feel it is a bit over the top, you would rather remember him for his politeness than have a child kicking and screaming , having a tantrum and generally demanding attention for the wrong reasons! He is aware enough of other people to learn more about what is appropriate as he grows and sees other styles of behaviour. I am now looking back and wondering who thought I was a pain at the time!!