it was in specific comparison to things you have to roll for. Spells are magic, there’s no question that they happen, the question is what happens because of the spell, so you might roll for damage or to hit. in contrast, there’s a question whether you will lift the boulder (muscles are not magic) so you roll to check whether it’s even possible for you before determining the consequences (throw the boulder, roll to hit and for damage). so physical events tend to require checks to see whether it’s possible, but spells do not require this check, they simply occur because of the nature of magic.