Your first counterpoint seems unnecessarily picky.
> So while it is a suitable DSL for many things (it is also seeing new life in web components definition), we are mostly only talking about XML-lookalike language, and not XML proper. If you go XML proper, you need to throw "cheap" out the window.
But the TWE did not embrace all that stuff. It’s not required for its purpose. And to call it “xml lookalike” on that basis seems odd. It’s objectively XML. It doesn’t use every xml feature, but it’s still XML.
It’s as if you’re saying, a school bus isn’t a bus, it’s just a bus-lookalike. Buses can have cup holders and school buses lack cup holders. Therefore a school bus is not really a bus.
I don’t see the validity or the relevance.
As discussed in the thread, the author has not dove deep into schema validation, but the org does use it.
Ignoring that part of schema definition and subsequent validation is exactly why it seems "cheap" on the surface.
So, TWE is not using an XML lookalike language, but someone has done the expensive part before the author joined in.