Yea i heard something about that. when scream/legcut hits, the hp turns green (that means glacier). When the opponents glacier is low, the legcut will be more succesfull.
And it might also be effective with lower range weapons, like sword 1.5, ii 1,5. But mainly when u use glacier resistance, it will be more succesfull. Try it out in arena's, where u can use glacier resist etc. I 've tried it out in pk's, and the priests that got the glacier resist, din't got legcut or screamed.