Depends on the benchmarks, as 2070 is faster in most games unless you factor in few select games like Forza. Games that support DX12 are in favor of Nvidia.
So here is the issue with that argument. Where did MS say that it's GPU performs like a 2080 or even a 2080S for that matter? It has been disproved so many times in this thread, in the next gen console speculation thread, and several other threads. AMD favors high compute, high TF. Nvidia cards with HALF the TF numbers, are beating it. For instance 2060 can trade blows with Vega 64, while using much less power, and half the TF's. If you wanna go with that same logic, then 12TF on xbox series x would be comparable to a RTX 2060, going by TF numbers alone. If RDNA2 has, let's say 10% to 25% gains at max, then it would be comparable to a 2060S/2070. But then you have to take into account of power limits and TDP, which would drop it back down to near 2060S performance. Which wouldn't be a bad thing, but definitely not near 2080S just because TF's, that's a pretty stupid argument.