Firefox has got some kind of feature to take a peek at at a link by hovering or something... Now I understand the usecase.

… a feature which, at least for me, is rendered almost entirely useless by massive cookie banners that always cover the entire field of view of the hover. But, surprisingly, not in this specific case.

From an infosec/networking stand point, aren’t still actively loading the site? Whether it’s in a preview window or not?

Presumably the browser still has to fetch the page in that case, right? From a "surveilled net traffic" perspective, how is that different than clicking the link?