But that's silly. Why would Bethesda tell us there are 18 skills, only to come out with a surprise 3 or 6 more? They've said there are 18 skills, not that there are 18 skills at this time.
And when we consider those 18 skills, it makes sense that they would divide the skills evenly into combat, magic, and stealth. That's why each game since Morrowind has had a skill-count that's been a multiple of three. Otherwise, you've got imbalance.
And if there are 18 skills, 3 categories, and 6 magic skills, and we've accounted for 6 magic skills, then the -AFT skill is not a magic skill.
Never mind that menus are designed with grouping, and the -AFT skill is grouped with past- or confirmed-stealth-skills.