The specification change affects m15 R5 laptops, the m15 R4 systems seem to have the full core count. VideoCardz calls this an example of Max-Q optimizations gone too far. The GeForce RTX 3070 in the Alienware m15 R5 laptops has no reduction in clockspeeds, but cuts performance by about 10 percent via the reduction of 512 CUDA cores.
By disabling 512 CUDA cores Dell has reduced the performance of RTX 3070 Laptop GPU by 10%. There are no changes in the clock speeds. It is quite common for laptop manufacturers to use different BIOSes with pre-applied Total Graphics Power (TGP) to meet strict laptop thermal characteristics. What seems uncommon though is a reduction of GPU cores to meet the target.