Does the Attorney General have any authority to challenge a finding that a defendant has to pay a booking fee?

The Attorney General insists the issue is forfeited. (People v. McCullough (2013) 56 Cal.4th 589.) But McCullough involves factual, rather than legal, error. "[W]e may review an asserted legal error in sentencing for the first time on appeal where we would not review an asserted factual error." (Id. at p. 594.) In McCullough, the defendant did not challenge the trial court's finding that he had the ability to pay a booking fee, a claim of factual error. Here, the court's error was legal. It misunderstood the statute, believing the fee was mandatory, and said so expressly on the record.