When about children how can that be murky?
Billions and billions of photos and videos of children being touched, hugged, kissed, & played with by parents, family, playmates, siblings, friends, etc. The vast majority of images & videos of children aren't of them being sexually abused. Or abused in any fashion. Most people posting or emailing photos or film of kids online have no evil intent, whatsoever. They're just sharing pix of their kids. Not of their kids being abused.
It's should be noted, too, these moderators have God-Mode turned on. Which means they also have access to personal email, private clouds, etc. Things that people are doing -using Microsoft products- that are illegal. They're not actually intending to share their kiddie porn (or snuff films, or anything else). But because they're using a Microsoft product? MS has access to it. It's in the user license agreement. Along with MS's full cooperation with law enforcement. So if someone is flagged by police, and they get a warrant, & ask MS for access to their email / cloud / etc.? That's also where some of this is coming from. People just forget, the Internet isn't private. IDK why that just doesn't click with so many people. If it's online, it's accessible. Period.
So it's not just the posted content that mods are sifting and sorting through, but also all the stuff people are uploading to their personal accounts. Again, the vast majority are perfectly harmless / normal pictures & correspondence. And then there's a grey area (like someone filming their own abuse, to use in evidence for their divorce, not posting it publically, but still in the MS server farms. Or a journalist saving their work. Also in the MS servers). And then there's pure evil of many kinds. It takes real people to discriminate what's what.
It's not like the mods are only going image by image in sites clearly labeled pedobear or snuff.films.inc. They're looking at *everything*. Both flagged content, and investigative work.