>OK that doesn't have to do with blocking Google AdSense ads nor does it have to do with proxying so I'm kind of confused.
When a website wants to load an ad, it uses javascript[0]. The website can call a function in the included javascript file and tell AdSense "hey load an ad". If you simply block the JS file the website can break due to trying to call functions that don't exist.
uBlock (supposedly, I haven't verified this) instead of blocking the JS instead replaces it with it's own version. That version just basically says "yeah sure cool" whenever the website tries to display an ad, but doesn't actually do anything.
[0]: https://support.google.com/adsense/answer/9274516
