Check out the format for an inline style:

    {
      background: "red",
      fontWeight: "bold"
    }

It's just a Javascript mapping from strings to strings. That's a very un-powerful language, and that's what React consumes.

Sure, you could generate this mapping with all sorts of arbitrary code, just like how you could generate CSS with all sorts of arbitrary code. But that doesn't make the style declaration itself any more powerful, much less an arbitrary executable.