For determining the maximum performance achievable, the performance per watt is what matters, as the power consumption will always be limited by cooling and by the available power supply.

Even if we interpret the NVIDIA claim as referring to the performance available in a desktop, the GPU cards had power consumptions at most double in comparison with CPUs. Even with this extra factor there has been more than an order of magnitude between reality and the NVIDIA claims.

Moreover I am not sure whether around 2010 and before that, when these NVIDIA claims were frequent, the power permissible for PCIe cards had already reached 300 W, or it was still lower.

In any case the "100" factor claimed by NVIDIA was supported by flawed benchmarks, which compared an optimized parallel CUDA implementation of some algorithm with a naive sequential implementation on the CPU, instead of comparing it with an optimized multithreaded SIMD implementation on that CPU.