There are three stats: Toughness, Strength, and Agility. They do pretty much what you expect them to do. Among other things, toughness lets characters take more damage, strength increases damage and carrying capacity, and agility increases speed and dodging. Characters get higher attributes by leveling up various skills. You gain experience in a skill by performing that skill.
Here's the problem: a character with more agility will perform all actions more quickly: moving, combat, any trade skill, et cetera. It's not because his agility is necessarily more useful for those actions, it's more like an agile character simply lives in a different space-time continuum. Everything is faster for him.
Thus, a character with even a minor agility advantage will eventually catch up to and surpass any other character at any skill. Dwarves only have a finite amount of actual time between sleeping, eating, drinking, and going on break. A more agile dwarf will always perform more actions, and thus gain more experience, in that finite time frame. This will in turn increase his attributes more (including agility) which will increase his ability to perform mroe actions even further.
At this point, one might think "So what? That's the whole point of stats." My point is that the difference agility makes overpowers all other considerations: the difference is TOO big; agility is TOO good. In particular, consider a task like sparring. Dwarves will only spar for a finite amount of actual time. The sparring activity itself is not what grants experience in combat, but rather the number of attacks/actions performed determines experience. For example, each sword swing or wrestling move with grant more experience. A dwarf with a high agility will swing his sword many more times while sparring, and thus level up much than a less agile dwarf.
Thus, you run in to scenarios where a dwarf who has trained as a Record Keeper for a single season can then begin training as a Swordsdwarf, and that dwarf will quickly become a far better Swordsdwarf than dwarves who spent the first season training with swords. I don't see this as a problem with Record Keeping: any skill that levels agility will do the same thing. The problem is that agility itself is overpowered because it increases the speed at which the dwarf LIVES. It's like a permanent hit of dwarven crystal meth, and dwarves don't care about the resulting bad teeth.
(This is all true for adventure mode, as well, although the applications are more limited there.)