I think people are still confused to this day about CPUs, physical cores, and Hyperthreading which gives the impression that there's twice as many physical cores. The 2017 models of the Surface Pro had dual physical core processors with Hyperthreading so if you looked at Task Manager with all the visual aspects enabled you'd see "4" processing windows (the 2 physical cores + 2 hyperthreads).
The new CPUs in the Surface Pro 6 models are true quad core CPUs with 4 physical cores plus the 4 threads from Hyperthreading so it looks like you have 8 cores but of course that's now how it actually works out.
So yeah, having 4 physical cores + the hyperthreads, a big boost in performance over the 2017 models. Wish I had the money presently to grab one of the i5 base models in black but I can wait.