This article isn't specifically about privacy issues only, it's about promises that are being broken, which might be about privacy.
Some browsers either directly violate users by collecting telemetric data without consent, or you have to opt-out rather than opt-in, or they bounce around the Internet visiting places in the background without you knowing (using dns-prefetch or automatic updates etc.), using third party services that operates with a privacy policy you either cannot trust, or that are directly violating your privacy, or they have integrated third party software that do some of these things.