Any extension that's listed on the web stores have to be reviewed for malicious code, and they must do what the listing say they do. So if your browser extension has your passwords, then that extension would be considered a password manager.

The extension probably listens to the IPs of well-known time wasting websites like HN or reddit, then adds a latency to the browsing. Same with an ad blocker -- they know every site you visit but only to compare them with their blacklist of advertising IP addresses.

Of course, you have to trust they aren't doing anything else with that info, which you can probably assume you're mostly safe if you don't need an account to use the extension.