Yes, for that specific example it works. But in general, this essentially deletes the UL from the layout entirely. It won't be stylable[0] and it won't dispatch UI events that occur on it specifically.

One example of a reason you might want such an element to still participate in layout is to use that element as an area highlighter. Or you might make it a scrollable section; subgrid makes sticky-header tables rather trivial to implement now.

[0] Well, I can't remember right now if it's unstylable or if its height just ends up zero, but either way, it might not be what you expect.

One subtle thing worth adding is that display: contents also changes how accessibility trees are constructed. The element is removed from the visual layout and from the accessibility tree in many browsers, so semantics like list grouping, landmarks, or ARIA roles can disappear unless you re-introduce them manually.

That’s why subgrid ends up filling a different niche: you preserve the DOM structure, preserve accessibility semantics, and still let the children participate in the parent’s track sizing. It costs more than contents, but it avoids a lot of the accidental side-effects that show up once you start mixing layout, semantics, and interactivity.