Probably because there isn't a good definition of hard vs soft.
Personally I think there are really three types
Type one magic systems are highly limited and predictable, think allomancy, Action X equals result Y, with a limited number of X actions. For example, there are sixteen metals, or sixteen X actions, each one corresponding to a Y result.
Type two magic systems are predictable, Action X equals result Y with unlimited X actions, think Harry Potter, or Channeling in WoT. Each spell has a specific result, but no limit on how many spells there are.
Type three magic systems are not predictable and anything can happen: Gandalf LotR magic.
However, Brandon would disagree, and others would disagree with him