I mean it's absolutely possible and pretty trivial to do in-house online surveys so that you know whether someone has answered but can't immediately connect answers to individuals, especially if the survey didn't use an in-house web service.
Whether I'd trust a corporation that says some survey is anonymous is another matter entirely though, because I absolutely wouldn't
Finland is surprisingly corrupt (it's just not the sort of corruption where you bribe cops) and Finns are generally stupid and gullible enough to think we're not corrupt