And the consensus from the IAABO interpreters...including my esteemed friend and another board interpreter who has served on the NFHS rules committee...is that it's a typo, the IAABO signal should be labelled the same as the NFHS signal and it should be used for 5 second throw-in violations, as always.
Looks like a mountain out of a molehill, Billy.
My thanks to the IAABO board interpreters who post here.