Definitely multi coats in addition to primer.......my son has the Tricoat Pearl white on his '16 Malibu same as my '18 Traverse.....a few chips down to the grey primer.......GM touchup paint------shake for10 mins and still won't cover looks like bunch of sparkles in diluted milky snot and the grey primer pokes through.I thought the Tri-coat paints were a different process, hence the reason they call out the Tri-Coat. I think the tri-coat has one extra layer of paint on it besides the Primer, base coat, and clear coat.
But I could be totally off on this.
Only way to touch up small chips is: first coat GM Summit White to cover primer.......second coat GM tri coat Pearl touchup to add sparkles to the finish with exact match.....third coat GM clear coat to add depth and finish. Actually does a very good touchup this way.