I signed up to answer your worries here.
uBlock Origin ("uBO") blocks network requests from the browser before these network requests reaches Pi-hole.
browser => uBO => Pi-hole
This means that typically the number of requests shown as blocked by uBO is unlikely to change if you disable Pi-hole, as uBO can report only what it blocked itself, not what is blocked downstread by Pi-hole. Mainly the problem here is that you measured what was blocked, while you should be measuring is what is not blocked from your browser's point of view.
That sort of measurement is possible using uBO-Scope: https://github.com/gorhill/uBO-Scope. This extension will derive a score from the number of distinct base domain names for which there was a connection, and the ubiquitousness of those domain names for which there was a connection. It works independently of uBO, so it can be used to measure all sorts of blocking profile, including when nothing is blocked.
uBO-Scope will show you a list of all the base domain names for which there was a connection on a given page, you can use that list to assess different combinations: uBO alone, Pi-hole alone, uBO + Pi-hole.
Note that it's more of an experimental extension, so what I say above is assuming that uBO-Scope will be able to detect that a network request has been blocked by Pi-hole, this is not something I have tested, or something I am in a position to test -- but I am willing to have this fixed if needed, and if possible (uBO-Scope tests if the status code of the response is different than zero, it expects zero to be returned for blocked network requests).