Contrary to Dell's service manual, not all XPS 15 7590 machines come with the same heatsink. Only the Core i9 models appear to have full VRM cooling, with Dell equipping the other SKUs with a slightly lesser cooler. As its predecessors demonstrated, all XPS 15 need active VRM cooling, so why the penny-pinching Dell?
https://www.notebookcheck.net/Dell-is-equipping-the-XPS-15-7590-with-different-heatsinks-depending-on-the-configuration-you-buy.427869.0.html