i've learnt a lot in my life, i know i know how to learn, don't try to tell me i don't, dude!
eh, now seriously, my opinion reflects my experience as an artist(and martial artist). i really don't think you learn anything by repetition, in my experience, one learns by doing it wrong, paying attention, doing it wrong again, noticing what we're doing wrong, then not doing it wrong.
an example of the system in work: dwarves that could evade the weapon traps 100% of the time wouldn't learn anything new, they'd just repeat the same choreography over and over again, dwarves that get hit 90% of the time have much to learn, and would gain skill much faster. seems realistic to me
I feel you're playing down repetition just a wee too much. In most cases where people are expected to perform certain actions in highly demanding situations, they can't do what they haven't any practice in. Sure you can understand how it works, but putting it into practice through the body is another thing entirely.
Granted, repetitive actions do have a certain point where, they reach a limit. But even then, any new action you devise or create will need to be ingrained into the physical memory of the body through repetition. Unless you're a kinesthetic genius, repetition is the only way to make the body understand fast enough to employ it when it really counts.
How else would you explain people who play shooters all day every day become much better than people who don't, sports people who practice being better than those that don't, or the best musicians needing repetitive practice everyday to just retain that level of skill? Reflexes and muscle memory need time to develop, and be developed in a certain way in regards to the discipline at hand. You don't really need to think about what you're doing at all for these two things to develop.
As for the abstraction that happens during training, why not just assume that it happens when dwarves are put in the danger room? I think we all agree that engravers generally look at their past works and think about how to make their next etching better from those experiences. So why can't we assume that the dwarves who dodge the spikes do this too? Add this to the fact that the retention rate jumps up a significant amount when pain is involved in error, and the rate at which the dwarves train isn't too far off.
Thus, the word I think you're looking for isn't "real" but "believable". Is the DF world realistic? It certainly is quite deep in the mechanics it employs, but it doesn't mean that the overall game is aiming for a proper representation of the real world, all it means at that point is that the game is comprehensive in its scope, that the mechanics and representational values inside the game matches other values supposedly similar to it. In other words, it is a relation of factors based upon consistency and believability from the player's point of view.
Can pure repetition create a legendary practitioner? Probably not within the rules of this reality, but it's pretty dang close if given the amount of practice seen in DF. The person probably won't be very sophisticated in their approach, they won't have a wide enough array of skills and techniques within the discipline to be considered a master by a long shot, but what it does do is make the person extremely competent at what they do even if it is limited.