Firefox downloads a list regularly, it doesn't send URLs of every visit to Google https://feeding.cloud.geek.nz/posts/how-safe-browsing-works-...

"It would be too slow (and privacy-invasive) to contact a trusted server every time the browser wants to establish a connection with a web server. Instead, Firefox downloads a list of bad URLs every 30 minutes from the server (browser.safebrowsing.provider.google.updateURL) and does a lookup against its local database before displaying a page to the user."