More libraries than React work just fine with the existing Babel and/or Typescript JSX options. snabbdom is a big one to mind that isn't React/Preact, but there are plenty more.
The space that the Babel/Typescript JSX options describe is a constructive space for more than just React.
The library [0] I wrote that uses JSX converts expression attributes into parameter-less lambdas before providing them as function parameters or object properties. This is a different behavior than react's build tools or any of typescripts jsx options. But it's not inconsistent with the spec.
[0] https://mutraction.dev/