I think the text leaves not much room for further explanation, if you move more than once he can use the ability, if you only move once, he does not. And it is unimportant if your move limit is higher or not. you move first in fellowship, then in regroup, if you want, then, through radagasts abilty, even once more, in regroup, too, in both regroup phases, if you move again, he may choose to discard and draw
