VF series 1 were made from mid 2013 to late 2015 while series 2 was made from late 2015 to end of production 2017. Oddly, manufactures warranty which was normally 3 years, occasionally was 5 years and the last of the bread was 7 years.
So, your VF SV6 may still be under manufacturers warranty, if so simply get the dealer to look at it
If the vehicle is out of manufacturers warranty, considering Holden bounced around from 3, to 5, to 3, before the last VF's got a 7 year manufacturers warranty, i don't think it's fair you should suffer for it because you bought just outside one of their "5 year windows". So I'd push for them to consider it as a manufacturers warranty issue. But if the dealer thinks it's not a warranty job as warranty has expired, remind them that your Australian Consumer Law statutory warranty means what you buy should work for a reasonable time considering the price you paid. And since Holden was pushing commodores with longer than 3 year warranties at various times, for similar $, it's arguable that the statutory warranty expectation would be the same for all commodores (since they are all a similar product and similar price). And this is even more true when one considers statutory warranty usually has more reach than a manufacturers warranty. So, if they insist it's not a manufacturers warranty claim, you should insist and argue its a statutory warranty claim (or good will as Holden love to call it).
Though this sound like "effort" compared to checking MyLink plugs, it helps to educate ones self in their legal rights which may be much more helpful when/if more serious issues occur. Google ACL statutory warranty and NSW Fair trading for background. Consider it a challenge