Specifically, this is useful in global health situations where you have lots of data collectors with tablets entering data that all has to eventually come together. But has lots of offline/online changes and has an untrusted data entry issue where you don’t want anything deleted.
I don't get your use-case regarding data collection people, what exactly will a blockchain prevent them from doing? Are they all entering the same piece of data to then pick the version they all input the most?
In my use case you have say 5 people covering different territory collecting info that usually doesn’t conflict. Imagine doing a census of a few villages. You don’t want data changed or altered especially time stamps and want it to be shared across all nodes when they are in proximity so they can sync to a remote instance when back in coverage. In some situations it’s literally the group meets at a tree at noon with a coordinator that syncs up all the collectors and moves on to the next group.
There are some conflicts that need to be merged, but mostly just syncing lots of nodes asynchronously and you don’t want anyone dropping records, maliciously editing them, or accidentally overwriting.
Blockchain alone doesn't prevent you from modifying data -- just rewrite the entire chain. As an example, Bitcoin only prevents this with proof of work, but only following accumulated difficulty prevents someone from thinking my privately-mined chain is true.