This also seems like a class thing. As a working class Swedish Finn family, we ALWAYS assumed if they stay around dinner time, they would be offered food. Our parents were fucking heroes and so many of our middle class friends loved coming over because they knew they'd get food.
When we went over to their houses, it was always a big issue. Usually we would just leave before dinner, so that we wouldn't have to 'impose' on their dinner time. One time I remember, a friend of mine used to offer fruit to us when we were over. Yummy! A few weeks later he said their mother asked me to bring my own fruit, so from then on, whenever I went to their family, I had to remember to bring my apple.
LOL
This part of Swedish culture can absolutely be criticized and it is absolutely a thing that exists. I wouldn't know if it's the norm (I knew plenty other families where you absolutely would get fed, whatever time of day it was) but it definitely does exist. And it fucking sucks. It made me feel like shit as a kid to be honest and it created so many awkward things for kids, we had to TIME our hangouts so that I could get home to eat in time etc, because they just couldn't plan for one extra plate. (Some of these parents were also absolutely horrendous cooks, I realized later, when I was actually invited - so maybe they had a good reason?)
Swedish culture sucks. We are selfish, self-centered, self-indulgent and racist. Please critizise us every chance you get. Now that I think about it, many Swedes are just bad cooks. And yes, I've definitely had the 'can you stay and wait, we're just gonna have dinner' thing happen. It's fucking rude and awful.