It is NOT completely untrue.
Lets start with this
Microsoft confirms cheaper next-gen console will run One S versions with its own enhancements…
www.videogameschronicle.com
According to the article
Microsoft has confirmed that the Xbox Series S will not run Xbox One X Enhanced versions of backwards compatible games, and will instead run the Xbox One S versions of Xbox One and Xbox 360 titles with other beneficial features.
What you will get is enhanced versions of the games that do increase performance. That fix up frame rate and graphics issues that were present on the XB1S. The end result will be better than the XB1S for sure. But not at the level of the XB1X. For backwards compat most of the games will be 1080p. For next gen games though, you might get a decent number of them at 1440p, though most likely with dynamic resolution scaling at times.
In many respects the XB1X is more powerful than the Series S. Digital Foundry also claim this.
However what you say about what the Series is mostly true about the Series S specs. It's just your conclusion that I disagree with.
Lets compare the specs of both.
The Xbox One X is obsolete, but if you want to check its specs, go nuts. We have them right here!
www.windowscentral.com
The full specs breakdown for Xbox Series S, Microsoft's affordable new console headed into the next generation.
www.windowscentral.com
Thus my comment that the Series S is just a XB1S Pro still stands.
I do think a deep dive analysis of XB1X vs Series S for XB1 games will by very interesting to see once the Series S is launched. To see how much lower the Series S performance is and which extra features the Series S has that help it out.