This is a good thing. If executed properly, this suggests that the game has a high skill-ceiling.
That gives the game depth and breadth. Players gain (literal) experience playing, familiarizing themselves with various enemy types, getting comfortable with the physics engine, learning which strategies work best against which enemies, how to manipulate/traverse particular terrains, etc.
Once this knowledge base develops, the next step is the trend towards optimal strategies. The key here is that each individual player will find their own optimal way of doing things as they get comfortable with the game/controls.
Monster/enemy X may be most easily killed by combat method Y. However, perhaps the player is just really good at implementing combat method Z, thus for said player, optimal strategy might just be spamming method Z in the face of everything.
Replace combat/enemy with traversal/terrain and its the same applied concept.
The important thing to recognize is that MOST games already have this kind of system. HOWEVER, Aounuma's prodding is suggesting that this game will do this with a level of depth that isn't often or ever seen in Action/Adventure RPGs, which instead tend to focus on using in-game experience points to boost in-game skills - rather than allowing the actual human player to develop skills themselves via experience/experimentation. This, in theory, allows for much more unique experience, player to player, but also rewards experienced players - because their invested time/acquired skills will pay off (if you're good enough, you can kill things quicker, save more health, traverse areas fadter, tackle more difficult challenges earlier on, etc.).
This as opposed to a game like the Witcher 3 (which I adore and have put >650 hours into btw), where you level up your character more than yourself. Think about it; greater tolerance for potions, stronger/quicker attacks, enhanced signs, all of these skills are added by applying skill points, they don't require the player to actually learn something. The extent of learning for the player is attack pattern rhythyms for certain monster types and mastering the counter system. The skill curve is minor and the skill ceiling is low, Geralt improves becau6de you can overpower him if you play/grind long enough. In BotW - YOU will improve if you grind long/hard enough (think competitive Melee).
Of course this is all talk until we can actually play the game, but with what little we saw, this is the exact picture being painted IMO. Look at how many gifys we've got of different ways to approach tackling enemy types, adapting to & using the specific environment to fight monsters, using countless methods to accomplish the same task. It's all very encouraging. This looks like a genius game.
