You're right, of course. What we're really talking about is the fallibility of estimations (and arbitraging between them) - you can't raise your score as projected by an omniscient computing power, but you can as estimated by real engines limited by their fallibility (and AlphaZero is less fallible.)

Mostly I'm pointing out that these estimations represent the best guess of an ultimately limited engine. People tend to treat those engine evaluations as actual numbers, like scores in a sport like baseball or some such, but they're not.