Do they have any other option than to stick to their guns on this one? That's sold the XBox Series S as having feature parity with the Series X. If they go against that now, then they've engaged in false advertising and will immediately get slapped with a huge lawsuit and/or fine, plus all the negative PR that comes from it.
They're stuck until the next console generation, which is a long way out. And I wonder if PS5 will continue to gain ground against XBox for the rest of the generation as a result.
It will be interesting to see if they continue with their two-model tiering next gen, but I'm guessing they won't.