Ask an Aran thread.

No, Isaac, you would be wrong here. With the skill data ALONE, FullSwing is maxed at 20, but Overswing is maxed at 30. If what you said was true, Over Swing would be maxed at 20.

It should show Full swing (or over swing) in the skill book, and adds to the two hidden skills, FullDouble and FullTriple (with the over swing counterpart).

Edit: Also, OverSwing has Mastery books.

It doesn't. There is no Full Swing in my 3rd job skill list, but I still have the effects of full swing (I can tell because my second key press hits 2 times, just like Full Swing would).

 Spoiler

Now the earlier post was a theory to explain why I'm seeing what I'm seeing in game, I might be wrong about how this is hitting but right now it seems to match. If there's a quest for full swing later then lol yeah but I haven't seen anything about it.