Yep, that's a fact. In the past, avaricious laowei have chosen to ignore warnings about both individual training centres and blanket warnings about training centres in general here in China. Instead of making the big money they were initially promised, they ended up being used and abused. I can't say I've any sympathy for them. They have ignored the red flags and consequently deserve to suffer the consequences of their unjustified optimism.
As for Dongguan, it's got a bad name as a city of sin.