Do you agree that the information contained in the database associates your name with your survey responses? If so, then by definition it is NOT anonymous.
Do you agree that the unique link helps ensure that people don't take the survey twice? But in so doing, do you also agree that the unique link is also stored in the database, which associates your name with your survey responses? If so, then by definition it is NOT anonymous.
Do you agree that Dell could retrieve your information if they ever needed to for things like legal discovery, etc? For example, if someone said something really stupid like made a threat or something, which has happened before. If so, then by definition it is NOT anonymous.
Do you trust Dell HR and/or Dell leadership?
True anonymity severs any PII between the user, user ID, employee number, etc., from existence. It never creates it in the first place - i.e., no logs, no db entry, no links, no memory, nada. That's not the case here by virtue of the way it is created, distributed, and stored.
As to whether the 3rd party who manages the survey would give up that information, that's an entirely different discussion altogether.
But it is NOT anonymous by definition, End of Story.