Think the size of this incident prompted immediate reporting, so I'd trust it to be fairly accurate in scope, but typically statistical sourcing is done by UNAMA (cited in article) and I'd consider them authoritative and accurate.
To your point, typically the casualty verification (which UNAMA is tasked with) takes a very long time. Here's an example of three UNAMA reports stating three widely different casualty figures for aerial operations in 2011:
- 2011 report: deaths and injuries at 305 (pg 24)
- 2012 report: deaths and injuries at 353 (pg 31)
- 2014 report: deaths and injuries at 415 (pg 94)
These reports were released years apart and reflect revised figures for 2011. It simply takes that long to verify accounts and corroborate reports, reconcile conflicting information. It will take years to get a definitive confirmation for this incident.
Here's something seen in the UNAMA reports that's more harrowing than drone weapon releases mentioned in the article. When a drone operator merely reports activity, a typical response to it is that the local forces send out a team to investigate the location. They do this at night. Vehicles pull up, spotlights come on and distorted loudspeakers come on shouting screams at people to stay inside and wait. Disoriented and confused civilians, trying to make sense of the noise, do what any normal human beings do, which is go outside to see what this is all about. At that point, even children get shot because they're contravening instructions. They become a number in a report.
This is death by process.