Let's be honest adding 16 CU shouldn't increase the size by more than 50mm2. Keep in mind that this GPU doesn't have GDDR6 PHY and memory controller just HMB2 PHY or 8 CPU cores with L3 cache and other things, yet It is supposedly 60mm2 bigger than Xbox. Does Xbox One have FP64 capability or not?You cant measure dedicated GPU die size from Custom APU.
Xbox's APU dont have many unit that the dedicated GPU will have. Xbox's APU has less sophisticated display engine, no PCI-e root complex, probably no FP64 unit, less complex encode/decode engine, memory controller without ECC support, also probably less cache.
Either Xbox has much higher density or RDNA2 GPU has more units than 72CU or no HBM2.