To be strictly fair, the AMD Ryzen 7 PRO 5850U is a 10-25W TDP depending on manufacturer configuration, not nailed to 15W. Do cpubenchmark verify that it's running at a 15W TDP when coalescing the numbers?
There is no guarantee for that, but usually 5850U is used in ultra-thin laptops and they don't have enough cooling for more than 15W... For example, CPU in Thinkpad X1 Extreme GEN 4 is limited 27 WATT (at least models without vapor chamber) and it's a laptop with quite a good cooling and larger size.