If you look under the "Creating Magic Whatever" headers here they all say something like "Skill Used in Creation: Spellcraft or Craft (armor)." That's probably what they're referring to. With Craft(leather) you'd be stuck with the relatively few leather-based wondrous items.
If you're planning out a character in advance I suggest Craft(jewelry) which will let you do all rings plus the many jewel-based wondrous items. Plus even at low levels you can increase the value of uncut gemstones you find just by cutting them!