The "Cause X status on critical hit" passives generally only work on the ninja with said passives, not the entire team.

What is your point ? The passive procs only when Shikimaru hit a crit, the chance of landing a crit mean nothing - even if you have 99% chance but end up not landing a crit, you still don't trigger the Immobile.
And yes, I experienced the skill and it works correctly. Opponent's Shikimaru hit me with his mytery, landing a crit, my genjutsu bounce back the first Immobile but my character still got Immobile from the passive.