I had to purchase some JB Hi-Fi gift cards to maximise Amex point earn this month and they attracted SC, so it may only be the Coles ones that are excluded. I wouldn't be banking an upgrade in status on that though.
I learned this the hard way. Always got SC for spend on restaurant gift cards at Coles, in December stocked up on the coles/myers gift cards and got zero SC. Ironically you earn SC on any gift cards not associated with the Coles brand.
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