TBM parents burning garments

I'm 19, and I've been in the church my whole life. I'm just recently really starting to question everything, and while reading up on things I read that there's a specific way to dispose of garments. It sparked a memory of my mom using our sandpit to burn fabric. She sent me away when I asked what she was doing.

Is that legit? Do endowed people really burn their garments when they're old?