"The aim of the article is to show the principle and theory behind Dell's power policy and not a critique to its current application deficiencies. "
I'm sorry but it does indeed read like a Dell ad. It is well known that in real life, after a few minutes of high combined CPU+GPU load, Intel DPTF kicks in abruptly and heavily reduces the clocks, often lower than required, rather than smoothly reaching an operating point at the edge of thermal limits.
The borderline thermal design is also very sensitive to production faults. Out of the factory, a considerable percentage of XPS 15 obviously experience direct thermal throttling of the CPU and/or GPU under high load. This can be fixed relatively easily by repasting, however it is rather unfortunate to see laptops in this price range being shipped to users failing to perform the essential quality control steps.
Finally, the modding community at Notebookreview forum has shown that quite reasonable performance under full combined CPU+GPU load is possible without Intel DPTF kicking in within the same physical dimensions after certain modifications of the cooling system which allow heat to be more efficiently removed from the VRM area.