I'm on a Mac and just checked the Safari extension store. The only extension I see for Ublock is a fork of Ublock Origin called Ublock Safari. It hasn't been updated in a year, and is thousands of commits behind the official version.

It also isn't distributed by Gorhill, even though the extension lists him as the author in the extension store. In fact, none of this information is listed on the extension page itself.

I'm not sure the extension you're using is what you think it is -- I would be at least mildly cautious about installing it.

See also this issue (https://github.com/el1t/uBlock-Safari/issues/145) on Ublock Safari's Github filled with people complaining that the extension doesn't work and that Safari's tech restrictions mean that there aren't suitable alternatives.