I didn't even go Anti Form until after WtNW.

If you beat the game, it will also tell you how many times you used Anti Form and survived.
Also, after Anti-Form is used, your Drive guage returns to zero, if you left the battle by exiting the screen, otherwise, it simply consumes the Drive amount of whatever form you wanted to use. Final Form also cannot trigger Anti Form, regardless of how high your Anti count is.