Following user testing, we set our sections as collapsed by default.
However, some lists have only one section, and when going into such lists it can look very odd to land on a single collapsed section. It would be a lovely little enhancement if you could set that Lists with >1 section have collapsed by default and lists with only one section are default expanded. (I'm aware that lists can have individual defaults set, but I don't think many users are aware of this despite training and documentation!)