The labyrinth function uses the state as a whole for entropy, and the previous output number as the input. The pair sorting in Pseudonym Pairs is continuous, each new person who sorts themselves moves another person, and so an attack is only possible when a majority has already sorted themselves. You then have billions of people, when the system has gone global, so you need to get a number that pairs you with another attacker, out of billions of people. If you were to succeed in attacking the social consensus mechanism, and could choose the order in which you process transactions, each transaction still relies on the labyrinth function, and the output from the previous one, and the probability that you happen to get a random number that actually pairs you with another attacker, is very low since most pairs have already have had to be formed (based on that pair sorting shuffles over time with each new person, if you attack early you will get reshuffled later) and at that point you have a lot of pairs.
So what you can do, if you hack the social consensus, is to process transactions, and then if you get a random number that, amongst a large population of honest people, pairs you with one of the minority of attackers (probability as low always, regardless of population size), you can pair the person whose transaction you process with that attacker.
I do not see that as a relevant attack vector, what are your thoughts?