This is confusing to me. The link describes narrowing the search space to ~136.17bit, but that is still far too large to be tractable. Do they get an additional

This is confusing to me. The link describes narrowing the search space to ~136.17bit, but that is still far too large to be tractable. Do they get an additional birthday bound on that somehow? 68 bits would not be insane, but I don't really understand what's going on here. I highly doubt they found a collision with a probability of 2^-136, unless they exploited some kind of bad RNG bug (in which case the probability is much higher, of course).