My understanding (as was explained by my compliance department at work) is that per EU law, omission of acceptance is on par with rejection. Many off the shelf cookie consent plugins used by websites will default to this behavior (including the one my work uses, despite being a US company).

Ublock does actually have an option to enable just hiding the popups.

In theory though, there's nothing requiring websites to actually treat a hidden pop-up as a rejection in the US, so i guess it doesn't hurt to explicitly reject instead.