My in-laws did lots of things that seemed odd to me, but their background was in catering so it may well have been me that was wrong.
They always, always put everything in a line of bowls in the kitchen and you had to serve yourself. There was literally one exception - once FIL cooked something really simple (I think something like gammon and chips) and dished it up, and MIL told him off! We, as visitors (even though we were close family) always had to go into the kitchen and serve ourselves first. When we came back, they encouraged us to start eating straight away and they would then go and serve themselves. They faffed a lot while serving themselves, so we'd sometimes have finished by the time we came back, at which point they would urge us to go back and take a second helping. They always made twice as much as was needed - MIL herself ate very small amounts and FIL about average, certainly not excessive amounts. I think they must have imagined that everyone else but them was an absolute glutton!
There was always wine, even at lunchtime, and since DH usually drove and refused to drink anything at all when driving, I was strongly urged to drink quite a lot. The only way to stop FIL constantly topping up my glass whether I liked it or not was not to drink any of it at all until the whole meal was nearly over.
MIL went on offering me cream with everything the whole time I knew her and she still cooked, even though I clearly stated every time that I didn't like cream. At least she didn't just put it on without asking. She even offered me cream with yoghurt, every time.
When we weren't actually eating a meal, MIL was constantly bringing out trays of various kinds of snack foods, depending on the time of day - cake, bowls of salty snacks, etc. If you didn't take any for a while she would hold the bowl or plate out to you and even if you said no thanks several times, it would still keep coming around again.
Anything that was buttered had far too much butter on it. My grown-up DC still refer to putting a lot of butter on something as Granny-buttering it.
If we stayed with them or went on holiday with them there was a full cooked breakfast every day and the bacon was always fried. I don't really like fried bacon so I asked if it would be possible to have mine grilled. One morning I wandered into the kitchen before MIL started cooking and I saw my bacon sitting under the grill waiting to be started... with a pat of butter on top of it!
The actual dishes and combinations weren't that weird, though they were usually a bit more elaborate than what I was used to from my family - it was as if every day was a special day. My MIL told me a method of making roast potatoes that I still use to this day and am very grateful for. I just get the sense that they associated food with kindness, and rejection of food with rejection of them.