Already linked the source few comments above; if you read it there are quite a few more links.
The problem with victim's accounts is twofold. First, there are many accounts, and what gets quoted are folks telling the stories of terror, not the ones who fled for eg religious reasons.
Second, when it comes to China, there's a metric ton of fake news everywhere you look. You look into a story about communist government destroying a church, and later it turns out the church was actually a church-owned commercial building raised without a permit. You read about concentration camps, and only after going through few hundreds pages you realize they are more like western juvenile detention centers. And so on, and so on.
Thus, we shouldn't blindly trust either of sides; there's way too much politically-motivated misreporting involved.