Of course, by using that word, it's usually assumed that my preferences obey some axioms, e.g. von Neumann-Morgenstern, which I doubt your wrapping satisfies in any meaningful way.

I certanly did not intend any such implication. Which set of axioms is using the word "utility" supposed to imply?

Perhaps check with the definition of "utility". It means something like "goodness" or "value". There isn't an obvious implication of any specific set of axioms.