Author here, happy to answer any questions. I never imagined a polyfill for http_build_url would gain so much traction. After 12 years, deprecating it feels like the right move, especially given the new options from the community and PHP itself.
The JavaScript world is littered with stuff comparing to which your patch seems like a complex project. See those examples: https://www.npmjs.com/package/is-odd https://www.npmjs.com/package/is-even https://www.npmjs.com/package/left-pad https://www.npmjs.com/package/is-whitespace-character https://www.npmjs.com/package/isarray
I don't believe any programmer is actually using these. isarray and left-pad are at least functions that didn't used to be in the standard library, to slightly excuse them.