To add more details: They are indeed 4-core parts in the Surface Laptop 2.
i5 (Consumer) = Intel Core i5 Mobile 8250U 3.4 GHz, 4-core
i5 (Business) = Intel Core i5 Mobile 8350U, 3.6 GHz, 4-core
i7 = Core i7 Mobile 8650U 4.2 GHz 4-core
That i7 is the exact same part used in last year's Surface Book 2, which is probably strong sign that the Surface Book 2 itself will see a refresh soon.