You will not take away a knife without severe/fatal consequences from any skilled knife fighter regardless of what martial system you use...
You can train up for it... get really good at it... and practice all day long... but all you need to do is make one mistake.
Thank God most folks who try to use a knife don't really know how to...but If I see some dude with proper knife fighting form in front of me well...
It's safe for me to assume it's no longer about "disarming."
William Hazen