The "vast majority" of SAT instances would be something like a SAT instance you would draw uniformly at random from some kind of distribution on all possible ci

The "vast majority" of SAT instances would be something like a SAT instance you would draw uniformly at random from some kind of distribution on all possible circuits. Making this idea rigorous is what k-random SAT is all about. It turns out that most randomly generated SAT instances in this way will lack certain features that tend to make industrial instances "hard," and in fact there is research on randomly generating random SAT instances which have those features and thus which are more difficult to solve. For instance: https://dl.acm.org/doi/fullHtml/10.1145/3385651 https://dl.acm.org/doi/fullHtml/10.1145/3385651