Looking at things in terms of ratios seems like an odd way of judging whether misinformation is a problem. If 0.5% of the sentences I say in a day are violent threats towards children that'd be a problem, right?
“Won’t you think of the children?” type questions are not very useful, imho.
In your case, no one (barring a few people employing child soldiers) think children are fair game to be hurt so the answer to your question is that yeah, 0.5% of statements which are violent threats to children is a problem.
Covid misinformation isn’t as clear cut - reasonable people asked about the lab leak theory while yet others asked why a vax was being rolled out without holding manufacturers liable for adverse outcomes.
We’ve had situations in the past when a new medicine caused children to be born with shortened arms and other birth defects. In this light, it is reasonable to wonder why we should trust a pharma company when they didn’t trust themselves.
But the linked post is not even about the correctness of misinformation - given something has been classified as misinformation, how often is it viewed compared to non-misinformation videos is what they’re trying to answer.
The question being pondered is that if the ratio is 0.5%, is disinformation really a problem?