Axes labels are not in math font

According to this gallery example, the legend is in a math font, but the axes labels, $x$ and $y$ are not. The available CeTZ manual examples show axes labels in math font.

How does one get axes labels in the math font in the recent gallery example?

This is a bug due to Single letter strings get parsed as italicized in math mode · Issue #274 · typst/typst · GitHub.