Actually, no one has ANY idea how Anti-Form works. I've tried testing the point system before, and it still doesn't always work as expected (as in, any fight against Xemnas should almost guarantee an Anti-Form if you've died twice and Continued). I've seen more evidence that you'll get Anti-Form if you get hit during transformation.

But, of course, no one here knows how to use the best Form in the game, so I'm not surprised that ignorance is widely abounded.

Then again, Final Form is slightly easier to use.