It's true.
They're a left-handed thread, and often have a spring-loaded pin protruding from the front sight base that indexes them properly and prevents them unthreading during fire.
Before trying to unscrew your slant brake, check to see if there's a pin in place. Also, depending on when your rifle was assembled, perhaps the slant brake was brazed or welded into place, per the '94 AWB?
I recently threaded my SAR-1's naked muzzle and installed a standard slant brake. I find it actually works as advertised, and dresses up the gun compared to what it looked like before.
The slant brake is used to keep the rifle's muzzle down during firing, it diverts expanding gas pressure upwards. Not a big deal in slow semiauto fire, but consider what real AK-47's with Da Switch contend with during full-auto fire.