Yea I mean, if you look at Tigerlake, 15W barely serves 4 cores. AMD has 8 because not only it's smaller but more power efficient too.
The decisions are probably arbitrary as well. Marketing, profits, performance all play a role. 8+8+2 is possible too, but will it make sense as a brand, perf/watt, and in revenue terms?
Golden Cove, unless they change the design paradigm it's likely it won't be more efficient in MT. The growth in transistors don't result in corresponding increases in performance.
I won't bet on ESF being a big of a gain as SF. 10nm Icelake process sucked, so SF had lot more potential. SF brought 20% gains. ESF, maybe 7-10% on top of that?