There are a bunch of these threads.

It appears that they are looking not only at whatever you sent, but what others have sent too and assessing the situation.

Chances are UA, like all carriers, hotels, restuarants, gets a lot of one-off claims. The real issue is whether many people got sick, how sick, whether they were traveling together and what they suffered for damages, e.g. how long in the hospital, how many weeks of wages lost and so on.

As others note, these are claims adjusters of a sort. People break their leg, get hit on the head by the steamer trunks others shove into overheads, get scalded by coffee poured in flight and all manner of stuff.