I saw plenty of people saying "Covid is less severe in Children" without any issue. The people who had tweets taken down were saying things like "Children can't die from Covid, open the schools, there's no risk at all" but ignoring that:
a) Children did in fact die b) Children did in fact bring Covid home from school which infected potentially at risk parents/other family members.
See also the lab leak hypthesis (and a good example when people talk about "banning ideas!") - if someone said "Hey, we can't rule out the lab leak hypothesis", that's presenting an idea, not claiming something that hasn't been proven is true and I saw MANY people posting that without issue.
When people said "It was engineered in a lab to be more deadly to humans, and it leaked out" that's stating something as fact that had no definitive evidence, and would likely result in a "This may be untrue" labels.