I mean, these are personal stories people have told me. That's my source. I've spoken with thousands of people about their childhood trauma from tons of different backgrounds, including foster children.
Look at child abuse laws in your state. How are they defined? Anything short of that is completely allowed as discipline. If you give me your state (or name an example state if that's too personal), I'll post the laws.
If you'd like a resource to verify that, either call your local CPS office or non-emergency police. They are public servants. Ask them. They will tell you. It's completely true. You can even put locks on your fridge and partially starve your kid as long as it doesn't threaten their lives.
And how would you know which one was the woman?