If I'm correct in the interpretation of the API, one must wonder why such an API was created in the first place.
If the API send the ScrollToTextFragment to the internet source to fulfill, in other words the search engine / server du jour sends back a page at the relevant content.
But why? This could have been handled exclusively *inside* the browser, as ScrollToTextFragment is essentially equal to a Find in Page text search.
There reinvented the wheel and broke it by sending a query outside the user's box for no reason.