VERY LONG ball and chain.
"The Emperor is with us, His sacred light shields us, and he has sent his wolves to watch over us."
As I remember it:
1. the screamer move close to the unit of goblins.
2. at 8" away the unit has to stop and the fanatics are released as normal.
3. once the fanatics have moved the screamers can continue moving.
So if the fanatics roll an 8+ then they hit the screamers and do damage.
the fanatic rules are quite specific so they cannot be abused by flyers which are everywhere nowadays.