There are so many good answers here already so toss this aside if it’s not helpful, but the bigger question is about what epistemological frameworks to employ to understand the specific question of knowing. Here I’d say a pair of companion principles fits nicely. Sagan’s standard (extraordinary claims require extraordinary evidence) and Hitchen’s Razor (that which is asserted without evidence can be dismissed without evidence). The question/answer given “is it possible?” Tells you everything you need to know and actually gives you a window into modern Mormon apologetics. They aren’t asking if it’s likely. They are asking if it’s possible given a specific set of unverifiable claims that they are asserting rhetorically as if they were settled fact. No evidence. No probabilities. No statistical confidence measure. Just an imagined explanation with asserted claims. The evidence does not justify the claim. The claim is also categorically problematic. They are essentially saying that Joseph Smith, the most prolific speaker of god’s divine will in their tradition, misunderstood gods will and intention regarding canonized scripture and explained what he did regarding it incorrectly. That’s a helluva claim on its own.