In contrast, the BW advice emphasises that it is the elements that the players bring, via the stuff on their PC sheets (setting details like gear and relationships; PC orientations in the form of Beliefs; PC capabilities in the form of Circles; etc), that is at the centre of setting. Everything else relates to, and has a purpose in service of, that stuff.
There is a risk with the BW approach. Whenever I mention that risk I also mention
@Campbell, because he's the poster who has articulated it most passionately. The risk is that the play of the game and the articulation of the fiction becomes "distorted" or even (to use a strong word) "corrupted" in service of player wish-fulfilment and pre-conceived character arcs. I think BW has devices to protect against this, most notably a very high incidence of failure for checks (compared to, say, any recent version of D&D). But it's still something to be aware of.
Indeed, BW has means to prevent players from preset arcs... but high failure rates isn't one of them.
The default difficulty is 2 successes; the typical competent starting skill is level 3, and rolls 3d6, each die of 4+ being a success. Primary skill will be 4, or rarely, 5.
the possible combinations: FFF, FFS, FSF, SFF, FSS, SFS, SSF, SSS. that's 4 of 8, 50%.
The next labeled difficulty is 3 successes needed. 12.5% for competent, but for the primary skills at 4, that's 4/16, or 25%.And that 4d on the Ob2 default difficulty? 11/16 success. or 68%...
doing the math; may as well leave it here FFFF FFFS FFSF FSFF SFFF FFSS FSFS FSSF SFFS SFSF SSFF FSSS SFSS SSFS SSSF SSSS
And that's before adding a die from a "Field of Related Knowledge" (aka FoRK) at 2-7, or 2d from FoRK at 8+. I've almost never seen a player not have relevant FoRKs for their areas of competence.
For comparison, the typical D&D 5E starting competent skill (or weapon proficiency) is +2 att and +2 proficiency, for +4 and the typical roll is for 15+, or, 50%. In focus area, that's +3 att, instead, for 55%. The next labeled difficulty is 20+... for 25% to 30%...
Burning Wheel's defense against planning is far more subtle...
1) Beliefs change. Being forced to change them is a potential failure outcome.
2) Attempting things hard enough that you cannot succeed is needed for advancement
3) Goals are encapsulated within beliefs, and thus can be forced to change.
4) what you raise is entirely based upon what you've used and how hard it was for your character.
4.1) skills under 4 require tests that are high failure rate without artha, and tests that are low failure rate.
4.2) skills going over four start requiring tests that cannot be passed without artha (needs more successes than you have dice from skill, help, FoRKs, and tools), and skil tests with high failure rates.
4.3) dice added by Artha don't count.
5) Artha (the three metacurrencies) are earned by use of your Beliefs, Instincts, and Traits.
5.1) some earns require changing the related Belief or Instinct.
The easiest way to foil a plan to become the Maestro de Fence is to simply not offer up occasions to fence competent opponents... because without competent opponents, you're not going to get those "can't pass" rolls very often. And if you don't want to lose on those? You have to spend Artha, and Artha isn't cheap. Every one earned has a price in terms of in-fiction actions to earn them: either a trait used limit your options, an instinct used by the GM to start you in a bit of a fix, a belief challenged and either you embraced the belief and took the costs of that, or gave in, played against it, and now have to alter it...
Also, if one spends enough Artha on a skill over time, there's an interesting side effect... at a certain number of each type spent, the skill "shifts shades"... it goes from being "Black" 4+ on d6 to being "Grey" 3+ on d6. Do it again, and it shifts to "White" 2+... the rules don't provide a further shifts. I've seen that happen once. I've seen several PCs start with a grey (S on 3+) skill.
BW characters can wind up with the concept being turned on end by things the other players have brought forth...
Mouse Guard, while simpler, has many of the same elements...
Oh, and the D***-move version of blocking the goal of becoming a maestro de fence? Sure, you find competent opponents... who opt not to roll all their dice. They go easy on you. You learn almost nothing.
On the other hand, the player can always use a circles roll to find a suitable opponent, then use a social skill to goad them into attacking in earnest... but that has
other disadvantages... like wounds and death.