No, if it's a good blocker it's blocking all requests and connections to wherever the ads are being served from. There's usually ALSO a level of cosmetic filtering for things that get past the blocklist or can't be properly filtered because they're coming from the same server as stuff you actually want to see, but with ublock origin set to strict and noscript set to allow only whitelisted sites, my page load times are way faster. Sometimes a shitty webpage will still 'wait around' for a second to try and get a connection from an ad site but it's not loading anything into memory.