Yeah it seems odd, and if Apple won't tell him or do anything, it might be because they can't: such as circumstances of an active police investigation.

We are obviously not going to get a fuller idea about this situation from a blog post, and while I won't assume that the author has done anything wrong, there have been similar stories in the past where the affected individual was deliberately withholding the whole, much more illegal, story.

Presuming his innocence: What could have happened here is that the gift card he's purchased has been marked as part of a scam operation. Apple gift cards are frequently used for "tax bill" and "police fine" scams in Australia (where they are sold there is often signage informing people of that.) So potentially this person is accidentally roped into that.

Also it's not entirely unheard of to purchase gift cards for long-time users (who would normally just use their linked credit card), as the cards are often sold in the retail space with a 10% discount, or can be redeemed as rewards through points/loyalty schemes.

With all that said, at this point if he's not getting anywhere, he should approach a lawyer, as they'd be able to petition on his behalf (whether that is to Apple or to the state of Tasmania.)