YouTube sends more requests with uBlock Origin enabled? [1][2]
My theory is, without the ads, there is more space in the webview to load video thumbnails, each item representing a video in the HTML document probably requires a handful of HTTP requests to load and pre-fetch their corresponding metadata. I would not be surprised if other websites react in the same way. I hope this is the case, but I am suspicious enough that I will investigate further how the ad-blocker affects these websites.