Where should they be “taking” funding instead?

In theory, yes. But if you follow the link and that leads to downloading the JS and running it, you’re already too late inspecting it.

And even if you review it once (and it wasn’t too large or obfuscated via minification), the next time you load a page, the JS can be different. I guess there could be a web browser extension for pinning the code?

The only practial alternative I know of is to have a local client you can review once (and after updates).

So the trick is to use the #fragment part of the URL, that is not sent to the server.

Of course the JS one downloads from the server could easily upload it to it, so you still need to trust the JS.