It could have still aired in Perth? Packer didn’t own STW9 and would not have the same control over that channel as the O&O channels. And it was apparently (citation needed!) still fed to the regional affiliates over a clean feed, so STW still might have got it to air. Or it might have been played off tape.
Also, although TCN ditched the show first, GTV Melbourne didn’t ditch the show until the last ad break when instead of returning to the show at the end of the ads it just went straight to the 9 ident and into an episode of Cheers with no announcement