I do believe there are a few that you must practice first, but then again I rather like this and was going to implement this more on my own MUD.
What stops someone from going out and hack'n'slashing all day, then just learning the cool ones that happened to replace the old? It encourages 'power leveling' or 'rocketing' and it's something I'd like to thwart, personally.
I'm actually looking to put skill levels in, with the percentage being much like experience.
This was a bit off the topic, but ah well. Anywho I don't think it's a bug, but I'd have to check.