Another part of it is that AMD's Zen core is a much more area-efficient design than Intel's Raptor Cove (et. al.) core. Raptor Cove is 7.43mm^2 (Intel 7, Excluding L2/3 Cache) while Zen4 is 3.84 mm^2 (TSMC N5, Excluding L3 Cache). Intel 7 and TSMC N5 have comparable densities, though the numbers have changed over time and it depends on the transistor libraries used, etc. AMDs core is close to a clean-sheet redesign and, as Gelsinger has admitted, Intel has lost design leadership.

The Zen4c core has a comparable size to the Gracemont E-cores, so they don't really need a separate design.