Where did MS say that RDNA was 25% faster? I don't remember seeing such numbers coming from their mouth or Sony's mouth. From benchmark tinkering (
https://www.eurogamer.net/articles/digitalfoundry-2019-teraflop-face-off-current-gen-vs-next-gen), RDNA 1 is, at worse and most of the time, 50% more performant per FLOP than GCN. And RDNA 2.0 should go even further.
Same for the bandwitdth, where does it says that Series S would have less bw than One X? One X has 326 Gb/s and we don't actually know for Series S. But if it picks anything from Series X, we could have a split pool with part being 560Gb/s and the other 336GB/S (both being higher than Series X
The only thing that might be true in your statement, is about total RAM, as Series S is rumoured to have only 10GB (vs 12 for One X).
But, SSD can largely make up for the difference and CPU is wildly more powerful.
Series S should end up being a much stronger console than One X could ever be, on all fronts, GPU (a bit) but mostly CPU and SSD.
Hence why One X has not valid market positionning anymore and needs to be removed.