On your idea that they are worried about Covid spreading particularly I think it’s more than worry about that as in some cases and posters have admitted they’d do it for a child throwing up etc
Or they think stopping a sickness bug from spreading is also important. It's not as life threatening, but the disruption can be huge (think about when it gets into hospitals). You might disagree of course.
I think it’s a trait they have and I don’t. Although I’m sure given people mentioning the number of phone calls the school gets and the amount of posters who seem very keen to phone up someone else would do it.
I think it's natural to assume everyone is working from the same underlying objective view of a situation, so differences in action must be due to people's different character traits. I think we all do that. I'm not sure we're right to though. I think you might be underestimating the degree to which different perceptions of the seriousness of covid spreading are relevant. I note you'll accept if someone is CEV as justification for calling - does that mean you accept feeling afraid of your individual CEV child catching covid as a reason to phone, but not feeling afraid of a general increase in covid cases, or your child's bubble popping, or anything like that? (You don't have to answer - I'm not trying to have an argument, I'm just interested.)
One of the hardest things about fighting this pandemic is that we all have to be inconsistent. On the one hand we have to learn to be fairly relaxed about the risk of catching covid, in order to send kids to school without going mad. On the other hand, for the good of the overall battle, we also have to behave as if we really care about the risk of covid spreading - so we're careful in other situations, and so we don't send our own children in ill. This forced inconsistency is not really natural or instinctive.