I wouldn't have guessed there's any benefit from hyposalinity for shrimp.
Bob's correct, be very very gentle adjusting their salinity. A two point difference in SG (i.e. 1.023 to 1.025, or 1.022 to 1.024 is enough to kill them instantly if they are not acclimated slowwwwwwwwwly).
I wish I didn't know that from experience..