Yes of course, Zen2 Van Gogh would always be a substantial CPU upgrade over the Zen+ Picasso that is present in the current 2019 Surface Laptops (those were very late adopters of Picasso APUs..).
What I meant by
cutting on CPU performance is relative to their competitors (Lenovo, Dell, Asus, etc.) which will be using Zen3 on Cezanne.
Is Microsoft willing to lose on CPU performance when compared to the other OEMs' laptops?
I also have some doubts over whether or not the volume of the whole Surface line justifies the development of a truly semicustom SoC, let alone the Surface Laptop. The "semicustom" Ryzen 3580/3780U on the Surface Laptop 2019 were just higher binned Picasso SoCs, and even the Vega 11 on the top model had already seen the light of day as the
embedded V1807.
OTOH,
that Subor console with a custom Zen+Vega+GDDR5 does exist..