The blade 16 is just cpu bottlenecked, nothing to do with gpu vram or TGP here. You can see the gap is bigger in favour of the Alienware at low resolutions. Strix point has horrendous cross CCX latency and is bad for dGPU gaming.
Once again, the top-of-the-line Nvidia GPU option isn't necessarily always faster than the next option down depending on the implementation or thickness of the laptops in question.