Hijinks for Syndicate Members

“Syndicate members earn XP equal to 50% of the gp value of hijinks they perpetrate successfully. On average, 1st level followers will earn 50XP per month from hijinks. Assuming that their leader manages to bail them out of trouble everytime they get caught, followers will reach 2nd level in about 25 months (two years). Most ruffians do not, in practice, live that long.”

My question is: do syndicate members need to exceed their level’s GP Threshold in the same way the guild leader does?

No, they do not have to exceed their monthly GP Threshold. Doing hijinks is quite high-risk and sufficiently adventurous that it bypasses the GP Threshold requirements.