Fate Core has 18 skills while Condensed has 19, with Academics being the extra. Why does Condensed have the extra skill when Core does not?
I don’t have a definitive answer, but I can give you my opinion. In Fate Core, Academics is combined with Lore into a single skill. In our Fate games the skill list is more about the setting and style of play than anything. We take some liberties with the list of skills. We have a lot of magic and mythology in our games, so both “Lore” and “Scholarship” get plenty of mileage, it makes sense to keep them separate.
If you are simply wondering why the “Condensed” version has a longer list than the non-“Condensed” version–I think calling it “Condensed” is really more about the page count than the skill list.
When an focus plays a significant role in a game, it makes sense to split it between two skills, like Shoot and Fight, or Physique and Will, or Notice and Investigate, just so one character can’t just max out one skill and be awesome at that focus. So, it makes sense to split the supernatural from the scholarly. In a magic-heavy campaign that I’m planning on starting, both Academics and Lore will be used heavily by the practitioners, but one is more “engineering” and the other more “theory” - if that makes sense. We’re going to use Lore to cast the spells, and Academics to understand them.
Fate Condensed was produced in tandem with Fate of Cthulhu (https://twitter.com/fredhicks/status/1265707002543706112?s=20), which differentiates between academics (mundane knowledge) and lore (arcane knowledge). In most games where magic is used, having a single skill combined all forms of knowledge (mundane and arcane) when combat skills are divided in three concepts (athletics, fight and shoot) and social skills are divided in four concepts (contacts, deceive, provoke, rapport) can feel unbalanced.
Bear in mind that it just a default list, that you can customize as you wish. Some people like to combine deceive, provoke and rapport into one skill (influence). Others like to remove resources. Fate is super flexible.