[Skarg]

You're right. The rule specifies, just so pithily that one might question it means what it says:

"It succeeds unless the victim makes a 4-die saving roll vs. his IQ."

I.e. No casting roll. And yes, the 5 MH range is a clue since it would almost never succeed even at 2 MH if there were a Thrown Spell roll involved.